There seems to be a fundamental discussion on the abilities of POP3. The RFC is available via Google: Post Office Protocol - Version 3 There is explicit reference to the DELE Command which marks the message for deletion. However, this delete is not actioned until the connection enters an UPDATE state (usually by disconecting). This is something familiar to S60 users. I believe (but open to correction) that by default Modest does not issue an UPDATE state request and therefore this action would not happen unless the user manually chooses to disconnect an account. The normal expected Use Case for POP3 client interaction would be to run through AUTHORIZATION state then TRANSACTION state (including marking for deletion) then UPDATE state (to perform required actions including pending deletions). I suspect that the issue here is that Modest is either not passing the DELE action to the POP server. If the QUIT command were not being issued then this might also cause the issue but network sniffing would be simplest route to discovering this issue. Despite several comments this is a TRANSACTION command in the POP3 command set and not one of the optional POP3 Commands. My conclusion is therefore that this is technically a bug or a usability issue if someone can find a means to manually disconnect form a POP3 connection in modest and find the markers enacted as expected. Any comments?