[exim-dev] Bug? Exim rewrites domain in response to CNAME, …

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Autor: Max Bowsher
Datum:  
To: exim-dev
Betreff: [exim-dev] Bug? Exim rewrites domain in response to CNAME, in contradiction to what is written in Chapter 31
Hi all,

I believe that I have discovered a bug in Exim and would like to double
check whether the behaviour I am seeing is actually incorrect, or just
surprising.

The potential bug is:

When attempting to send mail to @domain1.tld, which is a CNAME to
domain2.tld, which is in turn a CNAME to domain3.tld, Exim reroutes
foo@??? to foo@???.

This would seem to be in contradiction to paragraph 3 of
http://www.exim.org/exim-html-current/doc/html/spec_html/ch-address_rewriting.html
- :

"""
One situation in which Exim does not automatically rewrite a domain is
when it is the name of a CNAME record in the DNS. The older RFCs suggest
that such a domain should be rewritten using the “canonical” name, and
some MTAs do this. The new RFCs do not contain this suggestion.
"""

The actual domain1.tld that I discovered this behavior with is
bcidahofoundation.org (I am not affiliated with them, I was just tasked
with working out why an Exim server didn't seem able to send mail to them).

At the time of writing, the DNS records in question look like this:

;; QUESTION SECTION:
;bcidahofoundation.org.         IN      MX


;; ANSWER SECTION:
bcidahofoundation.org.  900     IN      CNAME   www.bcidahofoundation.com.
www.bcidahofoundation.com. 84397 IN     CNAME   bcidahofoundation.com.
bcidahofoundation.com.  69      IN      MX      10 mail1.bcidaho.com.
bcidahofoundation.com.  69      IN      MX      10 mail2.bcidaho.com.


;; ADDITIONAL SECTION:
mail2.bcidaho.com.      83995   IN      A       207.170.246.155
mail1.bcidaho.com.      69      IN      A       207.170.246.146



Max.