I have indicated that I have been running my mail server on a Cubietruck.
It is running well enough for the past 270+ days since last boot. It
supports 4 domains and receives ~5K messages per day, most spam. There
are around a dozen users of this server. So not a big server, but what
may be common for in a SOHO environment.
My one complaint is how the anti-virus scanning software can temporarily
tie up both cores. This is sometimes noticable when I (or one of the
other users) send an email (via imap - dovecot) and wait frm some
seconds until the message starts to upload. Since getting mail is
typically a background function, delays caused by big anti-virus scans
don't show. Same with the actual receiving and sending of mail by postfix.
So I would recommend using a 4 core board, like the Wandboard, and
somehow limiting the anti-virus software to 3 of the cores so one is
available for actual mail work. I don't know how to limit services to
specific cores so this would work. I suppose that even on the
Cubietruck, you could limit the anti-virus to one of the cores. Perhaps
Cubietech will actually come out with their 4 core server board as they
have hinted at on their site, and we will quickly have a uboot to
support it. Until then the Wandboard looks really good (and I think
there is a BananaPi or OrangePi that is a 4 core with sata).
Of course it may be once I get Centos7 running with this software mix, I
will be pleasantly supprised that things are better scheduled so that
imap uploads do not get held up by other tasks like anit-virus scanning
of big attachments.
Or someone here will show me a simple way to change service priorities
to get things working better.
I think this is the only real performance issue I have on my server.
But then I have not tested DANE yet either...