There is so much scaremongering about running mail servers that it almost looks as if interested parties are trying to dissuade people from running servers using this well-known open protocol and instead tell them to use whatever proprietary or single-sourced product. In reality running a mail server is not difficult at all, it hardly takes resources and once configured it tends to run fine without needing much in the way of maintenance. The main pain points seem to be the need to configure a bunch of DNS records for things like SPF and DKIM. Spam is solved using a filter like Spamassassin and possibly a graylist so that boogeyman is vanquished for now - I'm still waiting for the next wave of LLM-generated spam which is less easily recognised for what it is, this far is has not shown up yet. You may need to add some exceptions to the graylist for some of the bigger, non-standards-compliant services like anything run by Microsoft and you may need to use a "smart server" - an SMTP proxy for outgoing mail - if port 25 is blocked on your connection but these are not hard to configure.

I've been running my own mail services for close to 30 years now starting with handcrafted Sendmail configurations, now running Exim and Postfix. Running your own mail services isn't the scary problem it is made out to be.