Dear Dominic, thanks for your interesting comments. I administrate the Postfix mail server, not the Exchange, so I can't do anything to implement DKIM in the second one.
In my Postfix mail server I've just have SPF implemented for outgoing mails.....Maybe it's better to add DKIM + DMARC in place of onl DKIM ??? Thanks a lot again. El mié., 6 nov. 2019 a las 13:48, Dominic Raferd (<[email protected]>) escribió: > On Wed, 6 Nov 2019 at 16:12, Roberto Carna <[email protected]> > wrote: > > My cooperative mail server is an Exchange which does not implement DKIM > at all. > > But also I have a Postfix mail relay for the "example.com" domain. > > Is it possible to implement DKIM only in my Postfix server for all the > outgoing @example.com mails ??? Or doing this I affect the outgoing mails > from my Exchange server because it sends @example.com mails withouth DKIM > mechanism ??? > > It is possible, but in my opinion pointless. In fact DKIM without > DMARC is problematic at least, precisely because there are > organisations which send some emails conforming to one or other > standard (or both) and others emails which do not, and the recipient > cannot be confident that non-conformant emails should be rejected - > the very situation you have in mind. > > In theory adding DKIM to some emails should not cause any problems. > Might some recipient MTAs see that your domain has a DKIM record in > DNS and then 'downgrade' (treat as spam) or block emails from such > domain that don't have DKIM? I am not sure how big this risk is, but I > can't see you gain anything by running it. > > Are you sure your Exchange server can't implement DKIM? >
