[txtsd]

How do you deal with emails sent to gmail getting labeled as spam by default?

Also, qq.com and mail.ru block mails citing IP frequency limited and spam message rejected, respectively. I've found no way around these.

I just send one personal email a day, on most days.

[amaccuish]

I've never had that. My setup mostly did DKIM and all that for me. Never had mail arrive at the other end into spam. For incoming, I use rspamd. It's taken some training but it's a lot better now.

[txtsd]

My SPF, DKIM, and DMARC are on point. No idea why it goes to gmail's spam.

[acct1771]

Anticompetitive practices designed as strong security.

[krageon]

It's possible your emails are malformed or contain weird headers, that gets them flagged very heavily as well.