I have a personal mail server, but I find that other's anti-spam systems make
my email server almost unusable sometimes. In fact, one the only email
service I could reliably communicate with is GMail. Others block my emails
for reasons I could hardly fix. Most notably:
They block me because of anti-spam services (namely Spamhaus) which labels
whole IP ranges as spammers, because someone on that IP range did spam at
some point. I can't just change my IP network, so I can't fix this problem.
They block me because the reverse IP address doesn't correlated with my email
domain. I can't change that, only my ISP can, but it wouldn't bother doing
it for a home Internet user.
Both are awful reasons to be completely blocked by someone, keeping in mind
that I'm using DKIM, SPF and DMARC. This especially awful when I'm replying
to someone, so they know I'm not a spammer, yet they still block me for no
If you have your own mail server, please don't go crazy on the spam filtering
and think what you're doing before blocking at mass.