IMAP ports in Firewall

[courier]

Hi all,

What are the ports that I have to ask my ISP to keep open in the firewall
to operate courier-IMAP

I run Redhat 6.0 and 6.2 and I note this in my services file on
www.metta.lk

# /etc/services:
imap2           143/tcp         imap            # Interim Mail Access Proto v2
imap2           143/udp         imap
imap3           220/tcp                         # Interactive Mail Access
imap3           220/udp                         # Protocol v3

but there is no note on imap4

thanks
Jacob