Mail server options – Plesk 12
A choose of mail servers are available
Dovecot / Courier-imap
Postfix / QMAIL SMTP server
Additional Mail server options controlled in Plesk.
Maximum number of connections (IMAP, POP3, IMAP over SSL, or POP3 over SSL) Maximum number of connections for a user per IP address
Mail box outbound limiting is available.
Switch on limitations on outgoing email messages