It is normal for isp's to block port 25, this prevents many forms of spam
robots/viruses from operating. Basically back in the day port 25 was used
for incoming and outgoing email, and eventually someone realized it was a
security flaw and it was better to use a different port for the authenticated
So yes this is quite normal. Modern Email clients 'should' use port
587 and most do, but for historical reasons not all do, and most email servers
will allow either port for an authenticated user.
"Jon Koerber" <firstname.lastname@example.org> wrote:
After exhaustive debugging and testing, I have stumbled onto the problem.
It appears, for whatever reason, that when sending email out from my
development servers, PORT 25 fails?
If I change the email parameters to PORT 587, the email is sent almost
I have no idea why this is? On our production Application servers, they
all send SMTP to the same email servers via PORT 25 (not 587) and they all
Does anyone know why this might be this way? Is it a firewall issue on
the production email servers, application servers, or something else.
Or could it be that my local ISP is blocking outgoing PORT 25 traffic? I
can't imagine that would be the case since I am able to send and receive
emails via my normal Mac Mail client without an issue - unless Mac mail tries
multiple SMTP ports when trying to send mail?
Any clarification on this would be greatly appreciated.