From a command prompt, initiate a connection with the mail server.  Use port 143 for IMAP, port 993 for seucre encrypted IMAPs:

telnet 192.168.1.60 143
Authenticate to the IMAP server, specifying username and password:
A LOGIN username password
Chose a folder:
01 Select INBOX
Display  a message using rfc822 specifications.  Here message number 13 is listed:
02 fetch 13 rfc822

Logout to terminate the session

03 logout

 For more details, see RFC 3501.