I'm happy with it. Been running OpenSMTPd for many years at this point, on both OpenBSD and Linux, and I have no complaints.
I've also started using OpenSMTPD on linux machines when I need a simple MTA (which is to say, in almost all cases).
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I've also started using OpenSMTPD on linux machines when I need a simple MTA (which is to say, in almost all cases).