On 4/6/20 11:55 AM, Michael Orlitzky wrote:
Ok, you're right.
;-)
My suggestion to create multiple records was in response to the claim
that there are MTAs that will try a backup MX, but won't retry the
primary MX, which is false to begin with. Trying to argue against an
untrue premise only muddied the water.
I will not exclude the possibility of email sending programs that will
use backup MX(s) and not use the primary MX. But these are not general
purpose MTAs.
Back to the point: all real MTAs retry messages. You can find bulk
mailers and spam zombies and one or two java "forgot password" webforms
from 1995 that won't retry; but by and large, everyone does.
By and large, yes all well behaved MTAs do re-try.
The web form is a classic example of what a local queuing MTA is good for.
If anyone has evidence to the contrary, it should be easy to find
and present. If, on the other hand no such MTAs exist, then it's
quite pointless to run a second MX for the five seconds a year that
it's useful.
I disagree.
· I've seen connectivity issues break connection between a sending
host and a primary MX.
· Receiving side
· Sending side
· Breakage in the Internet (outside of the direct providers on the
ends)
· combination of the above
· It's not five seconds a year.
· It's more likely an hour or two a year, possibly aggregated.
· You can't control the retry time frame on the sending side.
· You can control the retry / forward time on secondary MX(s).
· Messages can be canceled while sitting in sending systems queues.
· It's much more difficult for someone to interfere with messages
sitting on your systems.
· Especially without your knowledge.
· It's /still/ considered best practice to have /multiple/ inbound MX
servers.
· Be it primary / secondary
· Anycasted instance
· Other tricks
· Do you want to tell the CEO that he can't have his email for 36
hours because you patched the mail server and the sender's system won't
retry for 35.5 hours?
My professional and personal opinion is that if you're serious about
email, then you should have multiple inbound MX servers.
--
Grant. . . .
unix || die
--
Grant. . . .
unix || die
