I recieve email but can't send unless i turn avast off

Running Window 7, With Office 10 and avast 5(lastest free one)
I can recieve emails but cant send unless i turn Avast off ever since the update?
What do i do to fix this? Sorry not a computer buff

Do you have a firewall?
Which is your email provider? Gmail?

Telstra. The only fire wall is what comes with Windows 7. All the other Avasts have worked with no drama’s.