quite a few of our mails bounce. They get rejected as SPAM. The only issue I can find with Mail-Tester is that the the avatar image still doesn’t contain an alt- attribute.
I contacted the known providers but the issue seems to persist. After contacting ATT for example it works for few days and then the mails bounce again.
Most of our users use the forum in mailing list mode and I wondered if the forum simply sends to many mails within a to short time frame.
I also found that digital ocean seems to have a spam issue.
What points should I check, too?