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Old 03-21-2006, 10:25 AM   #1
Registered: Oct 2004
Location: Romania
Distribution: Ubuntu server, FreeBsd
Posts: 472

Rep: Reputation: 30
exim - Could not complete sender verify callout

I am not very experienced with exim. In fact I used only sendmail and now I face a sever where exim is in action

On one of my servers I get a lot of rejected mails which aren't spams or other malware.

2006-03-20 16:31:09 H=( [] F=<> temporarily rejected RCPT <xxx@xxxancro
xax.xx>: Could not complete sender verify callout
I am using cpanel, but I would prefer to edit the configuration manually.

How can I disable the verifying process only for some domains?

Iíve read about:sender_verify, sender_verify_hosts , sender_verify_hosts_callback, sender_verify_callback_domains but I donít know how to effectively use them.

The whole process exim uses for verifying senders is a little confusing for me at this point. I would really appreciate if someone could explain to me how this works or point me to some good resources.

Old 03-22-2006, 06:05 PM   #2
Registered: Apr 2001
Location: Bremen, Germany
Distribution: Debian
Posts: 303

Rep: Reputation: 30
sender_verify runs the from address through the directors and routers and checks if they could deliver to that address. For local addresses this means the local part is checked for remote addresses this only checks whether the domain is ok in the sense that there's a (mail)route to it. Host exceptions are entered through the sender_verify_hosts.

sender_verify_hosts ! *.some.domain

verifies that the routers and directors know how to handle the sending address except for *@*.some.domain

sender_verify_hosts_callback does a lot more: it initializes an smtp connection to the remote site and sends HELO, MAIL FROM:<>, RCPT TO <the address to be verified>, QUIT. This is disabled by default since it's taking a lot of resources. To enable the host handling the from address must match all of


So, to exclude a certain domain from callback verification you could do

sender_verify_hosts *
sender_verify_hosts_callback *
sender_verify_callback_domains ! *.some.domain :*

(The :* can be omitted as it is implied when host list end with a negative item)

Unless you have a really small amount of mail to handle you should probably switch the callback off by default.
Old 03-23-2006, 03:09 AM   #3
Registered: Oct 2004
Location: Romania
Distribution: Ubuntu server, FreeBsd
Posts: 472

Original Poster
Rep: Reputation: 30
Thanks, a lot for your clear explanation


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