On Eudora, it allows you to limit the downlaod to any size file you want, say 20k. As a result, it only downlaods the message as the attachment is too big. That makes downloading over a slow connection go much quicker.

First, whether your computer automatically downloads an attachment, and whether it *executes* the attachment, are two completely different things. So your proposal really has only to do with download speed. I don't think this is a serious concern for two reasons: one, dialup is "dead", broadband is here to stay. Two, you can already get exactly this behavior by using web-based email (hotmail, gmail, etc.)

I like the idea, but mainly because there's a certain convenience in not being forced to download an 8MB file attachment over dial-up if it's not worth the download.

I don't know that the POP3 specs support mid-message aborts, but it could be accomplished by disconnecting and reconnecting to the mail server. Unfortunately, that would cause a significant delay in the download of each message.

I suppose people like me are better off using IMAP or a webmail interface.

I use hotmail.com and Yahoo. Both keep attachments on their servers till I ask for download. Both scan for spam and viruses. Both keep my address book and previous mail. I have three computers, but all this stuff is available to any of them, anywhere (assuming I can access the web).