I don't see how the prob;ems happening then, so ill make sure i understand what your saying, when you press the 'get mail' button, you get that error message, am i right?
And when you press the 'Write' button and press send after writting the mail, you get the other error message, am i right? (if so, set up outgoing settings for your ISP outgoing settings)
If so, try closing your firewall temporarily, then try sending/receiving the mail again, if no luck, try disabling avast temporarily
--lee