Thanks for the heads-up, Tim ...
On Sat, Feb 12, 2022 at 10:21:47PM +1030, Tim via users wrote:
Chris:
And what are some pros and cons switching to IMAP?
Wolfgang Pfeiffer:
Why should I need IMAP?
With `fetchmail', that I use, it seems I can even keep emails on the remote POP server - I usually just don't need that.
Although you can leave mails on a server with POP3, and just read newer ones, it's not designed for that usage pattern.
`man fetchmail':
------------- -k | --keep (Keyword: keep) Keep retrieved messages on the remote mailserver. Normally, messages are deleted from the folder on the mailserver after they have been retrieved. Specifying the keep option causes retrieved messages to remain in your folder on the mailserver. This option does not work with ETRN or ODMR. If used with POP3, it is recommended to also specify the --uidl option or uidl keyword. -------------
So it seems, leaving messages on the server after reading is not a problem for fetchmail, be it POP3 or whatever usage.
But yes: it might lead to problems ...
It can be very painful, and fail spectacularly. There's nothing stopping a server renumbering your messages, then there's no correlation between what you've already got and not yet seen.
Seems to be it. Again `man fetchmail':
---------- RETRIEVAL FAILURE MODES [ ... ]
A potential POP3 problem might be servers that insert messages in the middle of mailboxes (some VMS implementations of mail are rumored to do this). The fetchmail code assumes that new messages are appended to the end of the mailbox; when this is not true it may treat some old messages as new and vice versa. Using UIDL whilst setting fastuidl 0 might fix this, otherwise, consider switching to IMAP. ----------
The important part: "when this is not true it may treat some old messages as new and vice versa."
Which might mean (I'm guessing here), with another read on the POP3 server one might get already downloaded messages a 2nd time, while the new ones are not delivered, when running fetchmail again with the "keep" option ... might *hopefully* be fixed with the "--all" (something like "fetch everything") option while running fetchmail next time.
`man fetchmail' might be worth a read when considering POP3 or IMAP .. I really like the document.
I've used fetchmail most of the time in its default mode, namely deleting emails after retrieving them from the POP3 server. That's probably why I never, IIRC, became aware of any delivery problems with fetchmail while using it for ~15 or 20 yrs.
But true: setting up newly again my email accounts I might be using IMAP instead of POP3.
Thanks again, Tim! Wolfgang