My e-mail program is INCREDIMAIL (Portuguese version) and I hsve some accounts correctly configured there. The problem is: after some time, when the program tries to connect and send/receive messages, an error message appears indicating a problem and suggesting to check servers´configurations. So doing, I saw that servers´names have been changed without any personal action, generally including a <#> character and another ones. If then I change to the appropriate servers´names, the e-mail program comes back to normal operation.
What kind of error is this and how can I fix it?
The changes are not and error. These are needed in order for Avast 4.1 to scan the mail. If you can bring up a little patience wait for Avast to upgrade to 4.5 (tomorrow if everything goes well) and see if the problem is solved. Avast 4.5 has a different way for handling mail.
If you can’t/don’t want to wait, look HERE
In version 4.5 avast will have a new mail detection that will work automatically. Please, set up your email account just as avast does not exists. It will detect the pop3/smpt/imap ports and scan your messages.
Thanks a lot for both prompt replies. 
I´ll wait for 4.5 version and I hope it could manage e-mails without the disturbing effects above related.
Well, I´ve just updated Avast as below:
Last version - 4.1.501
New version - 4.5.518
I hope everything goes right from now.
Thanks again for information.