Email Issues (Off-Topic)

["Thomas J Hawley" tjh@xxxxxxxx]

** Reply to message from "Robert Holmgren"  on Sat, 5 Nov
2005 05:56:20 -0500

> > Deleting spam returns a minute GIF file to the sender confirming that
> > the spam arrived, which is to say, that the destination eddress exists.

> Wha??? How does that work? I DL my mail, I delete locally, and my client
> (Polarbar, or the tiny Rexx GetMail that I wrote) rebounds a GIF? No way. Or
> I delete on my ISP's mailserver, and that triggers the SMTP server to send a
> GIF?

If you open an html email in a mail client that renders the html (as opposed to
converting it to plain text), and if this email contains a coded reference to a
gif file on another server somewhere, then when the server gets the request for
this gif, it knows that the email has been opened because somebody's trying to
display the gif.

The easy way to prevent this is to work in plain text only, and never open
anything in html. Most mail clients can be configured to accomplish this.
Html email has other security vulnerabilities that can be avoided by sticking
to plain text.

There's just no way that deleting a message from an ISP's SMTP server could
cause the SMTP server to send a gif or anything else back to the sender.

Tom Hawley
New York
tjh@xxxxxxxx