OT: "domain-level" email hosting services?

[Jens John]

On Sat, 23 Oct 2021, at 16:21, Bastian wrote:
> The stack I use is exim, spamassassin, dovecot on debian 
> stable since ~2006.

If somebody would set something up new today, I would recommend the following 3-piece software stack:

1. postfix as the SMTP server and Let's Encrypt for a proper validated host SSL certificate

2. dovecot as the IMAP mailbox server

3. rspamd as the "policy engine". It can validate incoming SPF, DKIM, DMARC and ARCs which are all current best practice among the commercial email hosts, and it also can apply DKIM signatures and ARC seals to outgoing mail in a standards compliant way. The usual spam learning techniques are all implemented in rspamd, and it can interface with spamassassin, clamav etc as well. rspamd is very useful to prevent the piling up of different milters in postfix which work all differently.