VPN and timing out of the server

I seem to be having problems receiving and sending outgoing mail from thunderbird portable when VPN is up.
What could be the problem? When vpn is on I can not send or receive email.

It gives me the message:
"Connection to server timed out.
Sending of message failed.
The message could not be sent because the connection to SMTP server timed out."

I tried a couple different VPN's and so far only Ultra vpn sends the mail, but again it does not receive it.
It is also Ultra slow.

I tried the:

Tools>Option>Advance Tab>Config editor>Connection Timeout>network.ftp.idleConnectionTimeout=300
and it still dosen't work.

Does anyone have the solution for this? Thank you.