ot: fail2ban dovecot setup

[voytek at sbt.net.au]

thanks for all the help, I went back to the old server's config, and, it
worked as is, so that will do for now:

# fail2ban-client status dovecot-iredmail
Status for the jail: dovecot-iredmail
|- Filter
|  |- Currently failed: 0
|  |- Total failed:     5
|  `- File list:        /var/log/dovecot.log
`- Actions
   |- Currently banned: 1
   |- Total banned:     1
   `- Banned IP list:   1.144.106.60
#

Chain f2b-dovecot (1 references)
target     prot opt source               destination
REJECT     all  --  1.144.106.60         anywhere             reject-with
icmp-port-unreachable
RETURN     all  --  anywhere             anywhere