You can also add the file to the User Files (File, Add) section of the avast chest where it can do no harm and send it from there (select the file, right click, email to Alwil Software). No need to zip and PW protect when the sample is sent from chest. A copy of the file/s will remain in the original location, so any further action you take can remove that.
If you had avast send the file to the chest, then there is no need to add it, open the Infected Files section of the chest and send it from there.