It was one of those wonderful home IT support issues that show up from time to time.
My Mac suddenly stopped sending mail. It could receive mail, but not
send. The message was: "This message could not be delivered and will
remain in your Outbox until it can be delivered. Sending the message
content to the server failed."
Odd things have happened with my hosting provider in the past so I
just decided to wait for a day to see if things would clear up.
The next day nothing had been resolved and my wife had resorted to
using webmail to make sure the mail was getting out. Webmail was
working so it seemed unlikely that the mail server was down, just my
communication over port 25.
I look around in my mail settings and tweak a few things with no change in behavior.
I little googling later and it turns out that some ISPs have been
blocking port 25 to try and help with the spam problem. At this point
we are way beyond what mere mortals should be worried about. I can't
imagine working through this with my mom over the phone.
I started poking around on Qwest for information regarding blocked ports, but didn't get far.
Back to Google and I come up with this post on Mac-Forums: OS X Mail will not send replies
The thread meanders a bit, but the meat is in post #7 by DarthMoops:
Hey, I was poking around on the Internet some more. It looks like
many have had Mac Mail troubles with Verizon. The following seems to
have fixed the issue (so far).
http://expertmacintoshconsulting.com...;id=34;lang=en
Go to: Apple Menu > System Preferences > Network > Built-In
Ethernet > Ethernet TAB > Configure/Manually > Max Packet
Size(MTU)/Custon > set to '1492' > Apply
The referenced site seems to have disappeared but to my amazement changing the MTU from 1500 to 1492 solved the problem!
This is so obscure I can barely believe it. There were other site
that referenced this change, but most had to do with wireless
connections, whereas I am hardwired.
If being a geek wasn't your thing and you don't have a handy geek
laying around (like my wife does) - what do you do? Drag your computer
back to the store? Call the Geek Squad? Pave your system? Get a new
computer?
What is a normal person to do?