[fetchmail-users] Re: RETR with UIDL

[Sunil S. <sh...@bo...>]

Quoting from Matthias Andree's mail on Fri, Mar 03, 2006:
> > Please note that the change I am recommending is that fetchmail
> > *should* use RETR with pop3+uidl servers. Other pop3 servers will not
> > be affected by this change.
> 
> Yes, it's still 6.4.X stuff since it deliberately changes behavior for
> no good reason.

There is a good reason.

The advice being given to force fetchmail to avoid using "TOP" with
these buggy servers is to enable the "fetchall" option. The FAQ is
littered with this advice for various servers with variety of
problems. The problems with "fetchall" option are:

- "fetchall" cannot be used with "uidl"
- "fetchall" causes mails to be redownloaded if there is a line-hit
  while fetchmail is downloading mails. If there are consecutive
  line-hits, the same set of mails could be downloaded any number of
  times.

To avoid the redownloading of mails, one has to now probably add the
"expunge" option also. Finding the best value for "expunge" is a
problem itself:

- "expunge 1" is expensive. It will reconnect for every mail. Many
  mailservers may not like this too. However, each mail will be
  downloaded only once.
- "expunge 2" is less expensive. Mailservers may still object to this.
  Very few mails will be redownloaded.
- "expunge 20" is relatively cheap. Mailservers may not object to
  this. Some mails will get redownloaded. However, on a bad day, if
  you do get consecutive line-hits, you will still end up with
  multiple copies of mails.

In short, the user has to go for some sort of experimentation and use
a sub-optimal solution to get the mails(*).

The best solution (wherever possible) is to use "uidl" as mails get
downloaded exactly once. To use "uidl", one has to use "no fetchall".
With "no fetchall", fetchmail refuses to use "RETR".

> fetchmail 6.3.2 already introduced the (incompatible) "use RETR with
> Maillennium server" change because it was considered we'd rather screw
> some message flags and a LAST pointer rather than truncate messages.

I don't get this part. If the pop3 server is supporting UIDL and
fetchmail is running with the "uidl" option, why bother about the LAST
pointer and message flags? After all, even if the user is running
multiple fetchmails, all those fetchmails would be running with the
same configuration.

And, as has already been said, most standard interactive clients use
"uidl" anyway. So, they also will not get affected.

> Sort of. At least the ones that were reported do not delete
> messages if the connection is hung up without prior "QUIT" command.
> <http://lists.berlios.de/pipermail/fetchmail-users/2006-January/000220.html>

Jakob, please give more details about the Mercury server:

- its signature line
- its CAPA output
- whether it supports UIDL
- whether you are using it with "uidl"
and finally,
- your opinion on whether fetchmail should use "RETR" with "uidl".

-- 
Sunil Shetye.

(*) This need for experimentation is not documented now. Currently,
there is no entry in FAQ which says that if you are using "fetchall",
you should necessarily use say "expunge 10". FAQ O9 does talk of
"fetchall" and "expunge". But, it seems to be bad-mouthing "uidl" and
switching to IMAP4 is given as a better option than using "expunge".
However, this is a documentation issue and not related to the main
topic.