one MX with multiple A records

[Vu Pham]

IIRC, for such a configuration, sendmail will try all the results 
returned from the DNS server until it can send the email or temporarily 
stops that email and will retry the whole thing again.

For example, I set up a test mx record for example.com which has two 
hosts 172.16.254.11 and 172.16.254.12, both have same name 
mail.example.com which is also the the mx.( I turned off sendmail 
service on those hosts to see the error )

The log shows what I expect : sendmail tries making connections to both 
systems .

Jun  2 01:27:43 pluto sendmail[17007]: n526RP8r017003: makeconnection 
(mail.example.com. [172.16.254.11]) failed: Connection refused by 
mail.example.com.
Jun  2 01:27:43 pluto sendmail[17007]: n526RP8r017003: makeconnection 
(mail.example.com. [172.16.254.12]) failed: Connection refused by 
mail.example.com.
Jun  2 01:27:43 pluto sendmail[17007]: n526RP8r017003: makeconnection 
(mail.example.com. [172.16.254.12]) failed: Connection refused by 
mail.example.com.
Jun  2 01:27:43 pluto sendmail[17007]: n526RP8r017003: makeconnection 
(mail.example.com. [172.16.254.11]) failed: Connection refused by 
mail.example.com.


I have a particular client who has similar config but for some reason, 
my sendmail never tries the 2nd host. If it tries the first host and 
fails, then it will just retries later for the same host. Never try the 
2nd one.


Is it because of some dns problem ? I tried dig and it did return two A 
records for the MX record of that client.

Any advice is much appreciated.

Thanks,
Vu