Easiest way is if there is a web interface to your mail.
If not, you need to telnet into your pop mail server sort of like this,
comments in brackets
open a command prompt and type:
telnet your.pop3.mailserver 110 (replace your.pop3.mailserver with
the incoming mail
server from the servers tab of the
accounts menu option)
user username (replace username with the username from the account name
on the same servers tab)
pass password (replace password with your password)
list (which will list all the email in your inbox)
(make a note of the message number of the big message you want to
delete)
(probably 1 if I understand you. Each message will be listed with a
byte)
(count beside it so the big one should be very obvious)
dele n (replace n with the message number to be deleted)
quit (this will actually delete the message and close the telnet session)
Good luck.
Jeremy Pope.