Unable to send to Gmail accounts only

Just installed this plugin to send transactional mail on a new VPS host, got my Mailcheap email working on its own, and then found that none of the test emails from Post SMTP would get delivered to Gmail accounts.

Went through a bunch of troubleshooting with Mailcheap, as I could deliver to normal domains, but not to Gmail accounts. My usual transactional emails were being fired off to the domain account. Worked through and eventually went to turn on registration so I could sign up on my own site with a test gmail account and got the registration email to the gmail account.

Sent the Post SMTP test email again, and this time it actually got delivered to all my test gmail accounts! Turned off registration to see if disabling this option somehow killed the test functionality of the plugin, but nope, worked just fine.

So, moral of the story here is that if for some odd reason your test emails fail to send to Gmail accounts (especially after a server migration/change) but send to normal domains, just save your Settings > General page to rewrite, uh, something. haha.

Man, that was a dumb waste of a few days lol.