Lion Mail receives mail but will not send

Question

Suddenly my (1 year old) MacBookPro's Mail program will receive but not send to my gmail account.  When it trys to send I get the message:
"Cannot send messageusing the server smtp.gail.com:[email protected]
The server “smtp.gmail.com:[email protected]” cannot becontacted on the default ports.
Select a different outgoing mail server from the list belowor click Try Later to leave the message in your Outbox until it can be sent."
I have a MacBook Air on which the Mail program works perfectly.  I've verified that the MBA and the MBP are using identical settings. 
Any thoughts on what I should try next?

Answer 1

Just execute the three commands in three different terminals.
The IP-Number you connected to is strange. A reverse-lookup gives:
$ nslookup 74.125.53.108
Server: 192.168.178.1
Address: 192.168.178.1#53
Non-authoritative answer:
108.53.125.74.in-addr.arpa name = pw-in-f108.1e100.net.
That is definitively not google. Is it the same from both notebook? If not you have a dns problem on the MacBook Pro! It could be your local router or some kind of proxy of your internet-provider.
Try entering the IP directly. So, a forward-lookup (in terminal) should give the following IPs:
$ nslookup smtp.gmail.com
Server:                    192.168.178.1
Address:          192.168.178.1#53
Non-authoritative answer:
smtp.gmail.com          canonical name = gmail-smtp-msa.l.google.com.
Name:          gmail-smtp-msa.l.google.com
Address: 74.125.39.109
Name:          gmail-smtp-msa.l.google.com
Address: 74.125.39.108
Use one of the above IPs directly in Mail as your server for sending mail. Does this help?
If not: Did you try the "Connection Doctor" in the windows-menu of Mail? At which point it becomes stuck?