[loloquwowndueo]

Which one would you suggest using?

I’ve been looking at Stalwart to replace my old exim setup, wondering if it’s a reasonable choice.

[comex]

Another memory-safe option is Haraka, which I’ve been using for several years now. I recommend it but only for people who need extreme customizability. For everyone else, the customizability is a bit of a footgun, since you can easily end up with accidental open relays and other misconfigurations (as I learned the hard way).

[tptacek]

If security is your concern, Stalwart seems like a fine option, almost certainly better than Postfix.