Quite a few variables factor into where emails land once they are sent out. Sometimes they land in the "promotions" tab, or sometimes they go to spam/junk. Domains have different email health scores and people's inboxes are trained to "learn" how to receive emails from a specific domain, or certain types of emails, and there are many other things that can factor in where an email will land in someone's email account.
Have you authenticated your domain with Roster to improve your email deliverability? If not, follow this article to get setup.
Send test emails to see where they land
Once you have your domain authenticated with Roster's email service, it can also be helpful to run a series of test emails to see where the emails generally land by sending a test email to a handful of different personal email accounts.
Here's how you can send out test emails within a campaign email template editor:
If you are still unsatisfied with the results, please contact our support team for further assistance.