Gnus Manual - Expiring Mail Go to the first , previous , next , last section, table of contents . 6.3.9 Expiring Mail Traditional mail readers have a tendency to remove mail articles when you mark them as read, in some way. Gnus takes a fundamentally different approach to mail reading.
Gnus basically considers mail just to be news that has been received in a rather peculiar manner.
It does not think that it has the power to actually change the mail, or delete any mail messages. Unless you ask it to, of course. To make Gnus get rid of your unwanted mail, you have to mark the articles as expirable . This does not mean that the articles will disappear right away, however. If you do not mark an article as expirable, it will remain on your system until hell freezes over.