Email deliverability FAQs

Get answers to frequently asked questions about email deliverability, including inbox placement, bounces, and more.

Inbox placement

Is there any way to know where an email lands (spam or junk folders/regular inbox/promotions tab in Gmail, etc) when it gets sent?

Klaviyo can confirm whether the recipient’s mail server accepted an email, but not whether it landed in the primary inbox, a promotions tab, or a spam or junk folder. Klaviyo is responsible for sending your emails, but once these emails are in the hands of the inbox provider (i.e. Gmail or Yahoo), the messages are filtered according to each provider’s rules. All inbox providers have a built-in system that scans incoming emails, and automatically sorts them using complex algorithms that are not made public.

Do URLs that direct to a third-party site impact deliverability?

3rd-party URLs in emails can impact inbox placement if inbox providers determine the links are suspicious or malicious. Factors like the reputation of the 3rd-party’s domain, and relevance to the content of the email can impact how inbox providers view emails with these URLs.

Why are emails to my internal team getting blocked?

If you are sending on Klaviyo’s shared sending domain and emails to internal team members are being blocked, you may have an internal filtering setup that is blocking the emails due to the From Address and sending domain misalignment. Inbox providers may view this as a spoofing attempt, and block the email to protect your brand.

If you are seeing this issue, set up a branded sending domain (also known as a dedicated sending domain). If you are already on a branded sending domain and emails are still getting blocked, work with your IT team to allow-list your branded sending domain on your filtering software.

Blocklists

What blocklists have the most impact on Klaviyo’s deliverability and deliverability with different inbox service providers?

Blocklists can have different deliverability impacts based on the particular ISP. Gmail uses Google’s own systems to evaluate sender reputation and advises senders to avoid shared IP addresses on internet blocklists. However, other inbox providers may consider SpamHaus, as well as SORBS and SpamCop to a lesser extent. The impact of a listing depends on the receiving provider.

Klaviyo closely monitors SpamHaus listings as this is the blocklist that can have the most impact on deliverability. SORBs and SpamCop are also monitored but have much lower impact. The impact of other blocklists depends on the receiving provider.

Open rates

Why are the open rates on my account low?

Open rates allow you to measure customer engagement and monitor your deliverability and performance. If you are seeing low open rates, take the appropriate steps to improve your open rates in campaigns or flows. In general, suppression of profiles that have Never Engaged is the best first step to addressing low open rates. Klaviyo makes it easy to create a Never Engaged segment through the Deliverability Hub.

Why did the open rates for a specific domain drop?

If you notice that your open rates only suffer for customers using a specific inbox provider or email domain, you can take steps to improve your sender reputation for this group. You can exclude low-performing email addresses from your sending lists, and isolate engaged subscribers from the low-performing domain with a segment.

Compliance

My account was disabled by compliance, what can I do?

To protect all our customers, Klaviyo has anti-abuse measures in place and monitors campaign sends. Klaviyo will notify senders if their campaign performance suggests suspicious activity, and if there are continuous patterns that suggest potential abuse of the Klaviyo platform, the account may be disabled.

Your account may also be temporarily disabled after being flagged by our verification and compliance team. This typically occurs when a new account attempts to send to an uploaded list of contacts for the first time.

What is a suspicious email address and how do I remove that flag?

When an email address hard bounces at least once across the Klaviyo infrastructure, it is marked as suspicious. This means that even if they have not hard bounced in your account, they have previously hard bounced in another Klaviyo user's account.

Suspicious emails are automatically skipped from receiving emails. This is done in an effort to preserve your sending reputation, as well as the sending reputation of other Klaviyo customers since sending to invalid addresses can negatively impact both IP and domain reputation.

If you believe that a profile or profiles have been marked suspicious in error, please reach out to Klaviyo’s support team, and provide us with evidence of the email address still being valid. Make sure to include a screenshot of an email you received from the profile in question.

Please make sure that this screenshot clearly shows the following:

• The email address that has been marked suspicious.
• The timestamp of the email being delivered on a date after the profile was marked suspicious.

Can I remove the Reply-To email entirely or set up a way where recipients cannot respond to the email?

You cannot remove the Reply-To email in an email campaign. If you don’t want to receive replies, Klaviyo recommends that you set up a separate email that you do not monitor (i.e., no-reply@domain.com) and use it for your Reply-to email.

Is cross-brand consent collection allowed on Klaviyo?

You can collect cross-brand consent (e.g., for brand collaboration giveaways) as long as the language on the signup form explicitly and clearly states the brands that the visitor will be subscribing to. Here is an example of what such a signup form would look like:

If a customer consents to receive emails from another brand through your form, that brand can upload the consented customers to their own lists and include them in sends.

Transactional emails

Can campaigns be marked as transactional?

Campaigns cannot be marked as transactional, as transactional emails must be sent in response to an action the customer took. To request transactional status yourself, you need a paid account and a metric-triggered flow. Each email must be approved before it can be sent as transactional. Learn how to use flows to send transactional emails.

For a one-time message with transactional content, contact Klaviyo Support to request an exception for a list- or segment-triggered flow. Get approval before sending or adding past profiles to the flow. Creating or back-populating a flow does not make its emails transactional.

Bounced/blocked emails

My sends have consistently been getting good open rates, but recently one of my campaigns had a high bounce rate. Why would this be happening?

If the impacted campaign has a much larger recipient count compared to your previous campaign sends, ISPs may be blocking the email because they see spikes in send volume as a red flag.

Additionally, check if there has been an elevated amount of unsubscribes and spam complaints. If there has been an increase in either one of these categories:

• Clean your sending lists
• Implement double opt-in
• Send to engaged recipients

In general, suppression of profiles that have never engaged is the best first step to addressing a high bounce rate for recent campaigns. Klaviyo makes it easy to create a Never Engaged segment through the Deliverability Hub.

Do bounces affect deliverability?

A hard bounce occurs when an email cannot be delivered due to a permanent reason, such as an email address being invalid. Hard bounces can negatively impact deliverability and your sender reputation in the eyes of inbox providers. Klaviyo automatically suppresses any email address that hard bounces.

A soft bounce can occur for a temporary reason, such as when a recipient's inbox is full or their email server is momentarily down. Soft bounces can also reflect authentication or filtering problems. Investigate repeated soft bounces instead of assuming they are harmless or outside your control.

What are MM3 sends and why aren't my emails being delivered to some domains?

MM3 messages are emails that result in communications with a cellular device (e.g., pagers and cell phones) in a non-email fashion such as a received text message.

The United States FCC maintains a do not email domain list here. All domains listed on this FCC page are expected to result in some form of electronic communication with the end recipient being a cellular phone device or pager. Unsolicited marketing communications to these device types are expressly prohibited and Klaviyo will block sends to these domains.

Dedicated IPs

What Klaviyo accounts qualify for a dedicated IP address?

Not all accounts qualify for a dedicated IP address. To learn if your account qualifies for a dedicated IP and more details about the warming process, please reach out to your Customer Success Manager for more information.

Can more than one Klaviyo account share a dedicated IP address?

Multiple related Klaviyo accounts can all share and send from the same dedicated IP.

Does Klaviyo offer dedicated IP addresses for transactional emails?

If your account qualifies for a dedicated IP address, Klaviyo offers dedicated transactional IP addresses for transactional emails as well.

How can I view my dedicated IP addresses in Klaviyo?

If your account has one or more dedicated IPs, you can view them by navigating to Settings > Email > IP addresses. This tab only appears for accounts with dedicated IPs.

On this page, you can see each IP's address, email type (Marketing or Transactional), and current status (Warming, Active, or Inactive). Open the IP’s row menu and select View IP to view its details.

Branded sending domains

Is it possible to send double opt-in emails from my branded sending domain?

Once you set up a branded sending domain on your Klaviyo account, your double opt-in emails will be sent from your branded sending domain.

Can a domain be used with multiple different Klaviyo accounts? Does the new account need to warm up the domain again?

A branded sending domain can be shared by multiple Klaviyo accounts. If the domain has already been warmed, the new Klaviyo account does not need to warm up the domain again. However, it is important to note that the performance of all the Klaviyo accounts will impact the reputation of the branded sending domain.

Can a single Klaviyo account have multiple branded sending domains?

Yes. You can use separate branded sending domains for Marketing, Transactional, and Service emails. All of your branded sending domains must use the same root domain. You can have 1 active domain per email type, with a second domain temporarily used when moving to a new subdomain. To add a Service domain, inbound email must be enabled in your email settings.

Can I change my branded sending domain?

Yes. When moving to a new sending subdomain under the same root domain, keep your existing branded sending domain connected while you set up its replacement. Follow the branded sending domain setup guide and choose the appropriate warming process. To move to a different root domain, remove your existing branded sending domains first. The new domain then sends right away, without domain warming.

1. Navigate to Settings > Domains and click Add domain. Select the Email type you are replacing and enter a new, unused sending subdomain under your existing root domain.
2. Complete setup and publish the DNS records Klaviyo provides. Dynamic routing uses NS records; Static routing uses CNAME records. Include the TXT verification record and verify the new domain’s connection.
3. Open the new domain’s row menu and select Activate. Choose Move traffic with domain warming and click Activate. If you see a confirmation explaining that traffic will move gradually instead of these choices, click Activate to start that transition.

Klaviyo gradually moves sending to the new domain and removes the previous domain from your account when the transition finishes.

Will adding Klaviyo’s DNS records affect sending on other email service providers?

Use a sending subdomain that is not used by another email service provider. Klaviyo’s CNAME records or NS delegation apply to that subdomain, so they do not replace the records for another provider’s separate sending subdomain.

Click tracking domains

My links are being blocked by uBlock Origin. What can I do about this?

If your account is using Klaviyo’s shared click tracking domain and you are seeing links being blocked, you can set up dedicated click tracking. This feature requires a paid account.

Warming

How long does it take to warm up a branded sending domain?

Warming should be a minimum of 30 days with good performance to thoroughly warm your domain. Once you are seeing consistent open rates with a significant volume for a few weeks, you can begin to widen your sending practices (e.g., higher volume win-backs, etc.)

In general, suppression of profiles that have never engaged is the best first step to warming up your branded sending domain's reputation. If any deliverability issues come up associated with your domain then Klaviyo makes it easy to address this by creating a Never Engaged segment through the Deliverability Hub.

If I decide to pause sending, what is the maximum amount of time that a domain can go without sending and not having to re-warm?

Sending reputation during warming is heavily based on consistency between both sending volume and customer engagement. If you are trying to slow down sending, Klaviyo recommends using a more strict segment with fewer profiles instead of stopping overall.

However, if you stop sending campaigns entirely, you will need to rewarm the domain.

Do new click tracking domains need to be warmed?

Dedicated click tracking domains do not have to be warmed.

Email authentication

What are SPF, DKIM, and DMARC records?

SPF

Sender Policy Framework (SPF) is an email authentication method designed to detect forged sender addresses during the delivery of the email. SPF allows the receiving mail server to verify that emails coming from a specific domain were sent through an IP address authorized by that domain's administrators.

When an email is sent from an IP address that has not been allowed through SPF, the receiving mail server may reject the email, or divert it away from the primary inbox. Without SPF records you could not authenticate IPs using your sending domain, allowing malicious actors to easily impersonate your brand.

DKIM

DomainKeys Identified Mail (DKIM) acts as a digital signature that is added to the header of an email to further verify the identity of the sender. Receiving email servers will verify that the DKIM signature matches that of the associated sending domain. Since the DKIM signature exists in the header of an email, it will also remain when an email is forwarded, unlike SPF authentication.

DMARC

DMARC stands for domain-based message authentication, reporting, and conformance. It is a protocol that uses SPF and DKIM to determine the authenticity of an email, giving domain owners the ability to protect their domain from unauthorized use.

DMARC provides instructions to receiving servers about how to handle incoming mail. A message passes DMARC when at least one of SPF or DKIM passes authentication and aligns with the domain in the From Address. When a message fails DMARC, the receiving server considers the domain’s policy along with its own filtering rules; passing DMARC does not guarantee inbox placement. Domain owners can also use DMARC reports to monitor authentication failures.

Implementing a DMARC policy on your domain can help protect you from spoofing, limiting your brand’s and recipients' exposure to potentially fraudulent and harmful messages.

What are Klaviyo’s SPF & DKIM records and how can I add them?

If your account is on a shared sending domain, these records wouldn’t be necessary as your domain is not used for sending the email. The email is sent from a klaviyomail.com sending domain which already has the necessary SPF and DKIM records in place.

If your account is on a branded sending domain, the SPF and DKIM records are added automatically during setup through the CNAME records for Static routing or NS records for Dynamic routing.

What does misalignment mean?

Misalignment refers to the mismatch between the sending domain for your outgoing messages and your sender email address domain (i.e. your From Address). For example, if you send an email from sales@example.com and you are using Klaviyo’s shared sending domain of klaviyomail.com, these domains would be misaligned.

In this example, if example.com is protected by DMARC, your account will need to use a branded sending domain like send.example.com to meet DMARC requirements.

How does DMARC impact inbox placement?

The p-value in your domain’s DMARC policy tells receiving servers how you want them to handle messages that fail DMARC. It does not determine inbox placement by itself.

The values are:

• p=none: requests no specific action for messages that fail DMARC. The provider can still filter or reject them.
• p=quarantine: requests that messages that fail DMARC be treated as suspicious, often by placing them in spam.
• p=reject: requests that messages that fail DMARC be rejected.

Gmail/Google Workspace specific issues

Why is Gmail showing a suspicious link warning on my emails?

Gmail can warn recipients about links it considers suspicious or unsafe. Check the destination behind each link in your email, including links that use click tracking.

Also check your email authentication. Gmail can warn recipients when it cannot confirm who sent a message.

Why is Gmail flagging my emails with a “Be careful with this message” banner?

Gmail can display this banner when a shared sending domain does not align with the From Address, including emails sent to internal recipients. A branded sending domain can address this misalignment, but it does not guarantee that Gmail will remove every warning.

For both personal and business inboxes, check whether the message passes authentication and DMARC. To align your Klaviyo sending domain with your From Address, connect a branded sending domain under the same root domain as your sender email address.

Other common deliverability questions

What is sender reputation?

Sender reputation refers to the trustworthiness of your brand as an email sender. It is most often associated with your branded sending domain. Inbox providers determine your sender reputation based on your sending practices, and consider this when sorting emails in a recipient’s inbox. Senders with a positive sender reputation are more likely to have their emails delivered into customers’ main inbox, while senders with a poor sender reputation are likely to see their emails placed into spam or worse, not delivered at all.

Any domain (e.g., From Address domain, branded sending domain, click tracking domain, etc.) and IP address you use for your email marketing has its own reputation that inbox providers consider when determining your overall sender reputation. It is important to maintain a good sender reputation on the domains and IP address to have strong email deliverability.

How do IPs get blocked due to list bombing?

When Klaviyo sees a large number of form submissions within a certain amount of time coming in from a specific IP, it may be blocked to prevent list bombing. List bombing is a malicious attack where the attacker exploits a signup form or checkout page by making a large number of fake submissions, filling the associated list with emails and phone numbers that have not consented or are invalid.

If you are seeing issues with form submissions coming from a specific IP address, reach out to Klaviyo’s support team.

How long are double opt-in emails valid for after they’ve been sent?

Double opt-in emails are valid for 30 days after they have been sent. Customers will need to subscribe again if they would like to be added to your list and the 30 day window has elapsed.

What are the key metrics that impact my deliverability?

Monitoring your deliverability performance is important to help mitigate potential deliverability issues and effectively reach your audience. The key deliverability metrics that impact your sender reputation and should be monitored are:

• Unique open rates
  The number of individuals opening your email divided by the number of emails delivered (as opposed to total opens, which measures the total number of times emails are opened).
• Unique click rates
  The number of individuals clicking a link in your email divided by the number of emails delivered.
• Bounce rates
  The number of bounced addresses divided by the total number of emails sent.
• Unsubscribe rates
  The number of recipients who unsubscribe divided by the total number of emails delivered. These rates are measured on a per campaign basis, or you can view the list growth report for a particular list.
• Spam complaint rates
  The number of spam complaints about a particular email divided by the total number of emails delivered.

See our guide on email deliverability monitoring and performance metrics for information on how to track your performance across these metrics in Klaviyo.

Gmail and Yahoo sender requirements

What are Gmail's and Yahoo's requirements for senders?

Gmail and Yahoo began enforcing sender requirements in 2024. Requirements vary by sending volume and message type, but the following practices help your emails meet them:

• Remove Gmail or Yahoo from your from-address.
  Don’t use Gmail or Yahoo email addresses in your from-address. If you are using @gmail.com or @yahoo in your sender email, switch over to a domain you own.
• Set up a branded sending domain
  A branded sending domain allows you to send emails that appear to be coming from your brand and allows you to have better overall control of your sender reputation. If you are a bulk sender (i.e., you send 5,000 or more emails per day to personal Gmail accounts), learn how to set up a branded sending domain.
• Set up a DMARC policy on your root domain
  ‍DMARC authentication is a protocol policy that servers use to make sure emails are coming from a legitimate sender. DMARC policies are good practice because they protect the sending domain from unauthorized use by bad actors, and bulk senders to Gmail and Yahoo must publish a DMARC policy. A policy of p=none meets the minimum policy requirement.
  
• Align your from-address with your branded sending domain
  The domain in your from-address must align with the root domain in your branded sending domain to pass DMARC authentication.
• Make it easy to unsubscribe
  Bulk senders must support one-click unsubscribe for marketing and subscribed messages. Klaviyo automatically adds the one-click unsubscribe headers to marketing emails.
  
• Keep spam complaints low
  Low spam complaints are a key way to show inbox providers that you are a legitimate sender who follows deliverability best practices. Gmail advises senders to stay under a 0.1% spam complaint threshold, and reaching a spam complaint rate of 0.3% or higher may result in blocked sends. Visit the deliverability hub in Klaviyo to view your deliverability metrics, or try Google Postmaster Tools to monitor how your sending strategy aligns with Google's requirements.

Who is considered a bulk sender?

Some of Google’s sender requirements apply only to bulk senders: those who send 5,000 or more emails to personal Gmail accounts in a 24-hour period. Once Google classifies a sender as a bulk sender, that status is permanent.

If you’re not sure if you meet the bulk sender threshold, consider that:

• Google will include personal accounts ending in @gmail.com and @googlemail.com.
• All traffic from the same primary domain and its subdomains will count towards the bulk sender threshold, including transactional emails.

There are 3 main requirements that you’ll need to satisfy if you meet the bulk sender threshold:

1. Set up a branded sending domain with DMARC authentication configured.
2. Align your from-address with your branded sending domain.
3. Make unsubscribing easier and clearer.
   • Your marketing emails must include a method to unsubscribe in just one step. Klaviyo automatically adds the one-click unsubscribe headers to marketing emails.
   • There must also be an unsubscribe link in the message body, but that link does not have to be one click to unsubscribe.

How can I monitor Gmail spam complaint rates?

Klaviyo strongly advises that you set up Google Postmaster Tools on your domain so you can monitor your domain reputation and spam complaint rates, as Gmail does not provide spam complaint feedback directly to ESPs (email service providers) like Klaviyo. Note that before setting up Google Postmaster tools on your domain, make sure you have connected a branded sending domain to your Klaviyo account.

Why isn't the unsubscribe button in the header appearing on emails?

Klaviyo automatically includes one-click unsubscribe headers in marketing emails. Inbox providers decide whether to display an unsubscribe button beside the sender’s name. The headers can meet the one-click unsubscribe requirement even when the button does not appear, but your emails must also meet the provider’s other sender requirements.

Gmail displays the unsubscribe button only when a message passes its automated eligibility checks, which include compliance with sender requirements and sending practices. A missing button alone does not prove that your domain has a poor reputation. When investigating, consider:

• If you are sending from a new domain, increase volume gradually and monitor engagement and spam complaints. Continued sending does not guarantee that the button will appear.
• High spam complaints or low engagement can signal a sender reputation problem.

If your metrics show high spam complaints or low engagement, you should take action to improve your sender reputation.

If low engagement is affecting your sender reputation, suppressing profiles that have never engaged can help. Klaviyo makes it easy to create a Never Engaged segment through the Deliverability Hub.

Additional resources

Frequently asked questions about deliverability

How to clean your list to maintain good deliverability

How to remove spam traps from your account

Troubleshooting why emails go to spam

Understanding sender reputation

Understanding email deliverability