Unfortunately this does seem email client specific. For example, one of the clients accounts where this was happening had a link in the footer of their review request. When it was removed, the email went into the main Inbox.
Gmail maintains their own process for spam filtering and doesn’t give a lot of insight into why certain messages are filtered. They have some guidelines for avoiding their spam filter.
Testing some scenarios, I found that removing the https://www.castledefensetn.com/ link from the footer of the review request email caused the review request to land in my inbox rather than the spam folder. This could be for two reasons:
1. Gmail is pretty sensitive to linking to pages that collect user information (link). I’m not sure if this is the case, but it’s worth keeping in mind.
2. It’s not unheard of that a spam filter evaluates emails based off of the content of the page that is linked (to ensure that emails are not linking to malicious pages). The spam filter itself may be sensitive to linked pages containing information about firearms. I tried to find a specific policy for this, but I couldn’t find anything specific. Just a hunch.
The easiest way to remedy this would be for me to edit the existing CV templates to remove the https://www.castledefensetn.com/ link from the footer and see if this fixes the issue. We could also try submitting a bug with Gmail itself to get more information on this issue, though response time for these issues is quite long (typically months).
This document will help prevent gmail users being blocked or being sent to spam folders.