FiOS blocking outgoing work emails from home

[jvk01]

I'm trying to do tech support for my business partner who has FiOS at home. His outgoing emails from our work account are always getting blocked. At the office (ATT Uverse) it sends just fine, but once on his home network he is blocked from sending outgoing mail. Does FiOS require you to switch SMTP servers when sending from their network? I have the exact same account setup and have no issues on Time Warner.

Using Apple Mail on OSX Yosemite, outgoing SMTP port 465 with SSL on. Account is hosted at Secure Hosting. Web mail works fine.

Any advice on what to check for troubleshooting, including anything on the router we should look at? Obviously it's not my equipment but I'm the more tech-saavy guy in the office so if you send me some suggestions I can try to walk him through it. 

TIA,

jvk01

[CRobGauth]

Not sure about other providers, but I believe Verizon blocks outgoing SMTP to other mail servers. Its a way to block spammers using Verizon network.

[tns2]

No they don't block 465.  Only port 25.  Check with your provider.  AT&T?  Perhaps they have restriction on where you can send from.