timeout error

i am using thunderbird for a while, but now when i activate the option to scan outgoing mail (smtp)in avast, i’m sometimes getting an timeout error. (mostly when i’m sending files larger then 2 mb). When i deactivate the option in avast, no error occurs.
i can see a difference in the way files are sent. when sending mail with attachment and with the option to scan outgoing files, the status bar goes rapidly form 0% to 99% and then keeps hanging, when sending the exactly same mail without the scanning option the status bar goes slowly to 100% and mail is sent succesfully.

Increase the time out in the email client as well as in avast4.ini
This has been explained many times before.
Please use the search option before asking.