You must set the timeout of both email program and avast to the maximum.
e-mail programs used to be 5 minutes (300 seconds).
avast providers should be configured to more than this.
I can’t see a way to ‘by-pass’ the question of avast or from your email program ::slight_smile:
Of course, as you may know, packing the files (zip, arg…) will decrese the size of the files (in most cases).