Forum Discussion
How to unblock zip-file attachements in outlook 2016 (or 365)?
Untill recently we could zip documents and hyperlinks into a zip files and put them in attachment of an e-mail. Microsoft even suggested to do so in their "help". Recently this often does not work ...
If you are receiving an NDR back, the antivirus/security software on their mail server (or possibly yours) is blocking zip files and bouncing them back to the sender. Only the server admin can change it or whitelist your address.
FWIW, When Outlook blocks a file, it's client side - your outlook blocks it only for you. It would not affect the recipient.