Otdfbt

Sendmail Delivery Status Notification looks like this:

The original message was received at Fri, 8 Feb 2013 10:49:11 +0100
from host1.example.local [192.168.0.1]

 ----- The following addresses had permanent fatal errors -----
<name1@example.com>
 (reason: 550 Host unknown)

 ----- Transcript of session follows -----
550 5.1.2 <name1@example.com>... Host unknown (Name server: example.com.: host not found)
... while talking to mx.example.org.:
>>> DATA
<<< 450 4.7.1 <name2@example.org>: Recipient address rejected: Policy Rejection- Please try later.
<name2@example.org>... Deferred: 450 4.7.1 <name2@example.org>: Recipient address rejected: Policy Rejection- Please try later.
<<< 554 5.5.1 Error: no valid recipients
... while talking to mx.example.net.:
>>> DATA
<<< 451 4.7.1 Service unavailable - try again later
<name3@example.net>... Deferred: 451 4.7.1 Service unavailable - try again later 

This is all perfectly clear for me (1 bad address, 2 deferred by greylisting). But this is very confusing for my users: there's Error (panic); name2@example.org is valid address, but it is mentioned in Returned Mail, so it clearly wasn't delivered etc.

Is there any way to disable Transcript of session follows part of Sendmail's DSN? Ideally using some option in sendmail.mc. I hope it does not need to use this language resembling BrainF*CK, in which Rewriting Rules in sendmail.cf are written.

Sendmail 8.13.8 on CentOS5, but soon 8.14.4 on CentOS6

Basically you can't. You may be able to filter it out if you like with a global procmail script (or similar). But you may also try to

define(`confERROR_MESSAGE', `text')dnl

and see what happens. In mail messages generated by your systems, text will be prepended in these messages. By including something that provides more clues to your users, you may succeed in educating them on how to read this. You can use sendmail macros like $u in text; they are expanded. If you have a copy of the 4th edition of the bat book, this option is thoroughly discussed in pages 1027-1028.