Question about sendmail.

Question about sendmail.

[Tony Gogoi]

Hello,


We run a linux mail server which runs "sendmail". Users connect to it
using "Outlook Express". 2 questions:

1. A particular user sometimes receives the same messages more than once.
Could his mailbox have become readonly sometimes. If so why ?

2. The same user has "Autologout" entered in the "log file" of the mail
server.  How can this be eliminated ? Or is it a configuration issue of
the mail client ?

Thanks,
Tony

Re: Question about sendmail.

[Glynn Clements]

Tony Gogoi wrote:

> We run a linux mail server which runs "sendmail". Users connect to it
> using "Outlook Express". 2 questions:

First, I'd like to point out that sendmail (or any other MTA) is only
part of the equation. E.g. Outlook will only connect to sendmail when
sending mail; retrieval will be handled by another program (typically
a POP3 or IMAP daemon).

In a typical Linux mail server, the delivery chain for inbound mail
looks something like:

1. sendmail receives mail via SMTP, and feeds it to an MDA (commonly
procmail).

2. The MDA appends the message to the user's mail spool.

3. The user retrieves messages from the spool via POP3 or IMAP; their
mail client (e.g. Outlook) communicates with the POP3/IMAP daemon.

Outbound mail is likely to be handled by sendmail alone; i.e. it
receives a message via SMTP, and forwards it to other mail servers via
SMTP.

> 1. A particular user sometimes receives the same messages more than once.
> Could his mailbox have become readonly sometimes. If so why ?

The usual reason for receiving multiple copies of a message is that
one of the programs in the delivery chain successfully transferred the
message but was unable to reliably determine that it had successfully
transferred the message.

A concrete example: when mail is retrieved via POP3, and deleted from
the server, the server will only actually delete the messages upon
receipt of a QUIT command. If the client retrieves some messages,
marks them for deletion, then closes the connection without issuing a
QUIT command, the messages will be retained, and hence retrieved again
on the next attempt.

> 2. The same user has "Autologout" entered in the "log file" of the mail
> server.  How can this be eliminated ? Or is it a configuration issue of
> the mail client ?

I've never seen such an entry in relation to sendmail; however, the
following strings all appear in the ipop3d binary:

	-ERR Autologout
	Autologout host=%.80s
	-ERR Autologout; idle for too long
	Autologout user=%.80s host=%.80s

while these are from the imapd binary:

	* BYE Autologout
	Autologout host=%.80s
	* BYE Autologout; idle for too long
	Autologout user=%.80s host=%.80s

[Both ipop3d and imapd are typically part of the "imap" package.]

I suspect that this indicates that the client connects to the
POP3/IMAP daemon, retrieves the mail, then keeps the connection open
rather than closing it when it's done, so the daemon eventually closes
the connection. That would tie in with my comments above regarding
duplicated messages.

I don't what configuration options those programs have; my version of
the package includes no significant documentation (although that comes
from RedHat 6.2; the situation may have improved since, so check
whether your version includes documentation).

-- 
Glynn Clements <glynn.clements@virgin.net>

Re: Question about sendmail.

[Thomas Steudten]

That's true. However the imapd or popd delivered with Linux RH
are only simple daemons.
I use the qpopper which gives you a lot of configuration options, like
flush the mail from the server after transfer, before and without a quit.
I use this for modem dialin. Sometimes my client fetches the mails from
the server (>5MB) and the transfer breaks. So all the mail are fetched
again with the normal pop3d, but not with the qpopper daemon. Ok, there's
a risk, but that's not the problem.

> A concrete example: when mail is retrieved via POP3, and deleted from
> the server, the server will only actually delete the messages upon
> receipt of a QUIT command. If the client retrieves some messages,
> marks them for deletion, then closes the connection without issuing a
> QUIT command, the messages will be retained, and hence retrieved again
> on the next attempt.