Since the storm lots of people are bringing in their laptops complaining that they can’t send e-mail through their mail client. Nine times out of ten the reason for this is because they’re logged into a coffeeshop’s ISP which is different then their home/office ISP. If your outgoing (SMTP) mail server is set to use smtp.east.cox.net and the coffeeshop uses bellsouth as an ISP, cox is not going to authorise the outgoing mail. With Autoroute SMPT you can specify a list of SMTP servers and point your mail client to localhost. Autoroute will detect your connected ISP and use the proper server. You must have entered the server’s address into Autoroute for it to know where to try.

Link: Autoroute SMTP