If you’re finding that your emails are ending up in the spam folder before you’ve sent out to your customers, chances are that your From/Reply-to email address is a Gmail, Yahoo, or another free email address. Before you start sending to your customers, you’ll want to make sure that you have an email address that has your domain name. For example, you’ll want your From/Reply-to address to look like firstname.lastname@example.org.
To edit this from the campaigns tab, click through the steps until you land on the Message Overview menu. Here would be where you want to edit the From/Reply-To Email.
From a flow, click on the email and then edit. From there you should see the Message Overview menu where you can edit the From/Reply-To Email.
To edit the default From/Reply-To setting for your entire business, from the dashboard, click on the account dropdown in the top right and select account. Click on Contact Information > Organization and edit the default from Email/Reply-to email address.
If you're still having problems with your deliverability, contact support.