--On 8. september 2003 09:18 -0400 Dan Kolis <dank@hq.lindsayelec.com> wrote:
Although it is theoretically possible, using POP (rather than IMAP) to leave the mail on the server until you pull it again with POP, many servers appear to clear out the mail after POPing it.
The Client program users LIST and RETR to get the messages than DELE to remove them. The server/cloud program(s) don't do that. If you/anyone want to leave mesage a\on a POP3 MTA, selecting a client program (or writing one) to not DELEte them at your discression is potenetially useful.
A *lot* of POP-using programs have the "Leave Mail On Server" option.
And a lot of people have used "Leave Mail On Server" as a poor man's 1-folder IMAP, leading POP providers to implement mail retaining policies of the "RETR it once and it's gone, whether you DELEted it or not".
This is shown up in RFC 1939 (current definition of POP3) section 8:
.....In these situations and others, users and vendors of POP3 clients have discovered that the combination of using the UIDL command and not issuing the DELE command can provide a weak version of the "maildrop as semi-permanent repository" functionality normally associated with IMAP.
...........and in response, server operators are recommended to:
* Enforce a site policy regarding mail retention on the server.
Sites are free to establish local policy regarding the storage and retention of messages on the server, both read and unread. For example, a site might delete unread messages from the server after 60 days and delete read messages after 7 days. Such message deletions are outside the scope of the POP3 protocol and are not considered a protocol violation.
Just to show that we've "been there, done that, code in the field".
Harald