4. Paste the following command on a line after '.' and before 'exit 0':
iptables -t nat -A PREROUTING -p tcp --dport 25 -j REDIRECT --to 2525
This works for the other standard ports as well, here's what I've entered in the /etc/rc.local and I've made connections to the POP3 and IMAP4 host via the normal ports as well.
# This script is executed at the end of each multiuser runlevel.
# Make sure that the script will "exit 0" on success or any other
# value on error.
# In order to enable or disable this script just change the execution
# By default this script does nothing.
iptables -t nat -A PREROUTING -p tcp --dport 25 -j REDIRECT --to 8025
iptables -t nat -A PREROUTING -p tcp --dport 143 -j REDIRECT --to 8143
iptables -t nat -A PREROUTING -p tcp --dport 110 -j REDIRECT --to 8110
The only thing that does not work in Mercury/32 with Wine is the SSL/TLS and you can use STunnel for Linux to allow the MercuryC SMTP client to connect to a relay host and have the MercuryS, MercuryP and MercuryI servers support SSL connections. See http://bugs.winehq.org/show_bug.cgi?id=14797