laptop in a different city, receives email, but can not send email, like it did perfectly when home

laptop works fine at home, but  in a different city, receives email, but can not send email, like it did perfectly when home

When trying to send emails get   Error message is 0x800cccoE

for out, using smtp.cox.net              port 25    no SSL

Why does the lap top work at home but not send emails when not at home???

Do I have a setting wrong???

Thanks in advance.

Paul