If you’re finding that your emails are ending up in the spam folder when you're first getting started with Klaviyo, it may be the case that your From/Reply-to email address is a Gmail, Yahoo, or another free email address. Sending mass email from a personal address can cause inbox providers like Gmail, Outlook, etc. to flag your messages as spam, as this is considered to be suspicious activity.
Before you start sending to your customers, you’ll want to make sure that you have an email address that includes your domain name. For example, you’ll want your From/Reply-to address to look like firstname.lastname@example.org. This indicates to inbox providers that you are a legitimate sender with a legitimate business.
How to Change Your Default From/Reply-To Address
To edit the default From/Reply-To setting for your business, click on the Account dropdown in the top right and select Account. Then, navigate to Contact Information > Organization and edit the default from Email/Reply-to email address. Then, click Update Information to save your changes.
Change the From/Reply-To Address for a Single Email
For a campaign or flow email, click into the email and navigate to the Message Overview page. Here, you can edit the From/Reply-To Email.