Author: Sebastian Arcus Date: To: exim-users Subject: Re: [exim] Exim authentication as client and $sender_address
On 01/06/13 12:21, Jasen Betts wrote: > On 2013-06-01, Sebastian Arcus <shop@???> wrote:
>
>>>> 1. Does Exim authenticate as a client and send one message at a time by
>>>> default (and authenticate again for next message to be sent) - or does
>>>> it try to send several messages on the same authentication session?
>>>
>>> By default the smtp transport will send as many emails as possible,
>>> you can set connection_max_messages to 1 to limit this to a single
>>> email per connection, or you can create several tranports one for each
>>> user.
>>>
>>>> 2. If it tries to send several messages in one go after authenticating -
>>>> what does $sender_address refer to? Is it the sender address of the
>>>> first message which it tries to send?
>>>
>>> It's empty unless they all have the same sender. (same deal with all
>>> other variables in the smtp transport)
>
> I'm wrong here that pruning of the variables is done for each
> recipient, (not for each email) the transport only sees one message at
> a time. when it completes the TCP connection is recycled and passed to
> a new exim process to transport the second message.
>
> RFC4954 only allows (successful) AUTH once per SMTP connection so any
> subsequent emails are going out under same authority as the the first
> email.
>
> many (most?) smtp providers allow authenticated session to use any
> envelope or email header sender.
>
>> Thank you for the info Jasen. I've been using $sender_address in client
>> authenticator for smtp smart relay for 3-4 years now. I don't use
>> $connection_max_messages (yet).
>
> The troubles I've had with subsequent messages going through the wrong
> transport unrelated to your usage
>
>> Thank you for the info Jasen. I've been using $sender_address in client
>> authenticator for smtp smart relay for 3-4 years now. I don't use
>> $connection_max_messages (yet). These are sites with up to 10
>> workstations connecting to the internal smtp server (which in turn
>> relays to the provider's smtp server). I haven't had any problems with
>> this so far - as far as I know. Would this mean that I was just lucky,
>> and exim happened to be sending just one message at a time out of sheer
>> luck?
>
> what will mostly happen is that exim is doing immediate deliveries so
> the delivery process is spawned immediately for each message submitted
> if your internet conection, and smarthost provider are reliable this
> will always succeed. if they wind up on the queue instead they'll be
> delivered after the next email going to that smarthost.
>
> If you provider supports STARTTLS but only allows it to be used once
> per session exim will not attempt to send a second email out that
> connection, and so will re-connect (and thus authenticate) before
> each email. (this is acknowledged as a (minor) bug in exim and may
> at some future time be fixed (which may will hurt your usage))
>
> Most of the details can be found by reading chapter 3 of the spec
> (repeatedly if neccessary)
>
