Hi,

On 23.07.21 19:44, Xavier Beaudouin via mailop wrote:
Well had another domain with 10 priority, same bloody behavior...

Still don't understand why Microsoft does not implements RFC974 as it should...
(well Microsoft and the mail has been a loooong way to break all RFCs.... but...
in this case they are not good at all...).

Do you greylist or anything similar on the lower preference machine?

I have seen servers switch over to a higher preference MX for all kinds of reasons so fast it looked like they were tried first in the logs.


Regarding RFC974
   If the list of MX RRs is not empty, the mailer SHOULD try to deliver
   the message to the MXs in order (lowest preference value tried
   first).  The mailer IS REQUIRED to attempt delivery to the lowest
   valued MX.  Implementors are ENCOURAGED to write mailers so that they
   try the MXs in order until one of the MXs accepts the message, or all
   the MXs have been tried.

It's been a while since I looked at this, but isn't "SHOULD" a recommendation? I understand this collides with the next "IS REQUIRED", but...?


Regards,
Thomas Walter

--
Thomas Walter
Datenverarbeitungszentrale

FH Münster
- University of Applied Sciences -
Corrensstr. 25, Raum B 112
48149 Münster

Tel: +49 251 83 64 908
Fax: +49 251 83 64 910
www.fh-muenster.de/dvz/

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