I'm actually having a similar problem recently, although my messages are declined at the SMTP stage, "due to the very low reputation of the sending domain", which I attribute to the output of certain cron jobs being sent towards my own Gmail account — it seems like my whole primary domain name has subsequently been blacklisted a few weeks ago: * https://news.ycombinator.com/item?id=21340460 * https://mailman.nanog.or…
I have migrated to fastmail for all of my personal e-mail, which I have been pretty happy with. So far I haven't caught any legit email which has been categorized as spam and negligible spam that has made it through into my inbox (mailing lists notwithstanding--I sort them using automation rules). My one complaint is that there is no way to turn off their "thou shall not receive executable attachments" filter so I still need people to play the "set windows to show the file extension, change it to .txt, and then attach it" game when people want to send compiled code via e-mail.
In any case, it is certainly a much better situation than the gmail spam filter I used while in school, which had about a 10% chance of marking outside messages as spam--in fact it even started marking e-mails sent by my professor (via the university gmail) as spam...