Re: [exim] verify sender

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Author: Heiko Schlittermann
Date:  
To: exim-users
Subject: Re: [exim] verify sender
Hi,

Oliver Howe <ojhowe@???> (Mi 11 Dez 2013 11:11:08 CET):
> Hi,
>
> Is it possible for exim to perform a verify account test as described here -
> https://my.handsonwebhosting.com/knowledgebase/139/Mail-Error-451-Could-not-verify-sender-.html


> I have tried exim -bvs and can get part of the way there, for example
>
> # exim -bvs ojhowe@???
> ojhowe@??? verified
>
> # exim -bvs ojhowe@???
> ojhowe@??? failed to verify: Unrouteable address
>
> which is fine, but it says verified for an email address that does not
> exist -
>
> # exim -bvs ojhgsdgdgdgdgdowe@???
> ojhgsdgdgdgdgdowe@??? verified


It's verified. Exim does the routing steps, and if these routing
steps succeed, the address is verified.


> so is there a way for Exim to send a VERIFY ACCOUNT message to the sender?


There is no such message. I think, they use this term to describe the
process…

Exim is capabable of doing "callout verification". (They use this term
too, and they use Exim too at their primary MX.)

In your ACL setup you'll see some line

    require verify = sender


This checks the sender, roughly by doing "exim -bvs …"
If you change this line to

    require verify = sender/callout


you'll get the callout feature. But be sure to read about the callout
options and implications.

Somebody could put tons of mails (fake) originating from *@t-online.de.
T-Online uses some ratelimit for incoming connections, thus, you'll be
unable to send messages to T-Online for a while (typically 24h), because
of your high connection rate doing the sender verification callout.

We use

    require verify = sender
    [ bunch of other checks ]
    require verify = recipient/callout=defer_ok,use_sender
    require verify = sender/callout=defer_ok
    [ bunch of other checks ]



But even if you put these ACL in place, you still can't verify the
address with "exim -bvs", you need to ask for processing the callouts:
read about -bh, -bhs and try "swaks --pipe 'exim -bhc ..'"

Good luck :)

    Best regards from Dresden/Germany
    Viele Grüße aus Dresden
    Heiko Schlittermann
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