I have been using https://posteo.de/en from many years now. They are ad free, secure and an affordable alternative. Their web interface is poor but not a problem for me as I use email clients on all my devices.
One of my colleagues was using it for ~3 years now and is considering switching, as their anti spam is less and less useful. Some days he wakes up to 30-40 spam/scam emails not being blocked, while he also did miss important mails being filtered as spam. (There is no spam folder on posteo, they just don't deliver spam emails to your inbox. Keep that in mind).
When he tried to forward these mails to the email address they provide for reporting spam, he got an automated mail delivery system email, that he was blocked from sending mails to that address...
When he tried to forward these mails to the email address they provide for reporting spam, he got an automated mail delivery system email, that he was blocked from sending mails to that address...