Email not working......sometimes

Greetings,

We have 3 32gig wifi only iPads for our office. All three are configured for our email server with the same settings (except for the user id obviously). They work fine in the office and when I take them home, they work fine in my home wireless setup. The problem occurs when they are taken to the other two users residence. They each get the same message: "The connection to the outgoing server xxx.xxx.xxx.xxx failed" They both can received with nop problem, but they cannot send. However, as soon as they get in range of the office - everything is fine.

Is there a setting that anyone knows of for home wireless setups that would be blocking the sending of the emails? Their laptops, connecting to the same SMTP server work fine from their homes. And again, if I bring the iPads to my home, it works fine.

Thank you for your help.