The security solutions on the mail system make a line that you need to cross, but it doesn’t guarantee a success.

It’s a hard way to guess how good is the implementation on the receiver, like GMX, Libero or other big country providers with “historical” service that don’t care about them too much.

GMX is banned in many places for example.

I agree. Self hosted my email for over a decade and as long as you do the recommended SPF, DKIM and DMARC you have basically no problems.

Occasionally I turn up in spam when I email someone I haven't before, but that's usually due to the .ro in my domain and the forced text mode rather than html.

I've found problems only start occuring when you send transactional email. User signups, notifications, etc. Anything really automated.

I think people like to joke on self hosting email because there are a lot of moving parts and it was hard to diagnose why something went wrong. Until the last decade and early 2010s there were no all in one self hosted solutions that made it easy & available for most to do it.

> Occasionally I turn up in spam when I email someone I haven't before

Just proved my point.

Google puts random things in Spam, including ones marked 'not spam' or from otherwise reputable senders (like Github, despite receiving their emails for a decade). My monthly credit card bills occasionally are dumped in spam.

Its not really proof of much unless one is constantly getting junked

Back when I used GMail, Google would sometimes mark correspondence e-mails from Google staff as spam. Heck, I even had instances of responses to e-mails I had sent to Google staff marked as spam. Spam filtering is complex and clearly Google has (and continue) to tread a very fine line here.

Last week I saw the same behavior sending email from my work's Google Workspace account to my personal Gmail account. The email stays within Google, I'm logged into both accounts on the same computer, does Google think I am I spamming myself...?

Google's expense reimbursement emails were systematically considered to be SPAM by gmail.

Google knew this because they even issued warnings.

Still, using your own domain and machine is different.

Unless you've had an interaction with that email address it will be considered SPAM.

Wait until you get on MS blocklist with no recourse

Or on any other RBL because someone else in the same netblock (maybe) did something suspicious.