I've been trying to understand why emails I send to folks with Gmail addresses end up in their spam folder with a cautionary note added even if they create a filter to never send mail from me to spam. I thought it was a problem with my own domain host's mail system.

I just did a test sending email using Thunderbird and there was no spam warning when it arrived. Is this something to do with OAUTH2 that David said needed to be addressed in the next version of Pegasus mail?

Unfortunately, if it's a limitation with Pegasus v4.7.3, than this will be a sad day for me as I send emails to clients and others and they need to arrive in their inbox without any warnings. I would prefer to keep using Pegasus as it has so many features that I cannot easily find elsewhere.

Thank you to anyone who can confirm that this is indeed related to OAUTH2. Or is there a setting I need to change in Pegasus mail that's the culprit?

Happy holidays to all .... stay safe / stay well!

R

OAUTH2 is an authentication protocol so I don't think it should be associated with messages getting tagged as spam.
Was the smtp configuration in Thunderbird identical to that in Pegasus Mail (server, port, and SSL)?
In your smtp host configuration in Pegasus Mail do you have the "Use only SSLv3..." option enabled (it shouldn't be)?

Thank you for the reply and suggestion, Brian. I don't have SSLv3 enabled. I'm still wondering what causes the issue. I'll test again with Pegasus and check the Gmail email's RAW headers for spam rules that are triggering the spam warning.

R