IMAP Howto
IMAP has features that make it more useful to folks who check their email from work and from one or more remote locations.
IMAP allows one to manage your Inbox on the server from each location. By deleting messages or saving to folders stored on the server, one will always be presented with the same message store.
To enable IMAP from your internet mail client, find the option for mail protocal and switch it from POP to IMAP. Leave the mailbox location prefix blank.
For example, for Eudora
go to Tools\Options\Incoming Mail
and check IMAP
Select the option for "When I delete a message:"
mark it as deleted
Thats pretty much it.
Deleting messages is a 2-stage process with IMAP. First you delete the message with the delete key or whatever. This will but a red X over the message or perhaps draw a line through the message header. But there is still one more chance to change your mind. The final irreversible step is to "Purge messages" (found under the messages pulldown menu in Eudora.) I think they also get purged when you exit Eudora.