Re: problem with mx ip selection on retries

On Tue, 2 Nov 2010, [email protected] wrote:

> 
> Hello Davide
> 
> I found an problem in xmail when re-trying to connect to mx with multiple
> ips
> 
> Here is a sample :
> Assuming domain XX.com have this dns setup
> 
> xx.com	mx 10	mx10.xx.com
> xx.com mx 20	mx20.xx.com
> 
> mx10.xx.com	A	10.10.10.1
> mx10.xx.com	A	10.10.10.2
> mx10.xx.com	A	10.10.10.3
> 
> mx20.xx.com	A	20.20.20.1
> mx20.xx.com	A	20.20.20.2
> 
> supposing xmail have now to send a mail @xx.com
> on first try it use mx10.xx.com at 10.10.10.1 : now the tcp connection don't
> work
> then os same first try xmail use mx20 at 20.20.20.2 : suppose tcp connection
> don't work too !
> 
> What i see in a trace is that for ALL the others retries for this mail,
> xmail retries ONLY on SAME ips, 10.10.10.1 and 20.20.20.2
> It never retry on others mx's ips !! And because there was no response from
> these two ips, mail bounced back to sender after all possible retries :-/
> (i checked the others ips, they responded correctly :-/ but xmail never
> tried them ...)
> 
> I think this is a major bug :(

Does not look like.  XMail would cache (in the MX cache) the *names*, 
which are mx10.xx.com and mx20.xx.com (and, for the duration of the TTL).
Then the names are resolved to IP addresses using OS specific library 
calls (getaddrinfo()).



- Davide


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