Zip Files being Blocked (Qmail)

Check whether the signatures file existing in the /var/qmail/control/. If this file existing then
check whether any statements in that file.

If there is any content, do the following:
vi /var/qmail/control/signatures
quick easy search and replace with vi using the following (Commenting the line in signatures file
):
%s/^/#/

Save and restart qmail it will work fine.