The pop3_version module, as its name implies, scans a host or range of hosts for POP3 mail servers and determines the version running on them.

msf > use auxiliary/scanner/pop3/pop3_version
msf auxiliary(pop3_version) > show options

Module options (auxiliary/scanner/pop3/pop3_version):

   Name     Current Setting  Required  Description
   ----     ---------------  --------  -----------
   RHOSTS                    yes       The target address range or CIDR identifier
   RPORT    110              yes       The target port
   THREADS  1                yes       The number of concurrent threads

This module requires only that we set the RHOSTS and THREADS values then let it run.

msf auxiliary(pop3_version) > set RHOSTS 192.168.1.200-250
RHOSTS => 192.168.1.200-250
msf auxiliary(pop3_version) > set THREADS 20
THREADS => 20
msf auxiliary(pop3_version) > run

[*] Scanned 13 of 51 hosts (025% complete)
[*] 192.168.1.204:110 POP3 +OK Dovecot ready.\x0d\x0a
[*] 192.168.1.219:110 POP3 +OK POP3\x0d\x0a
[*] Scanned 29 of 51 hosts (056% complete)
[*] Scanned 31 of 51 hosts (060% complete)
[*] Scanned 37 of 51 hosts (072% complete)
[*] Scanned 39 of 51 hosts (076% complete)
[*] 192.168.1.224:110 POP3 +OK localhost Cyrus POP3 v2.3.2 server ready >3017279298.1269446070@localhost>\x0d\x0a
[*] Scanned 51 of 51 hosts (100% complete)
[*] Auxiliary module execution completed
msf auxiliary(pop3_version) >