Gmail has some restrictions about which files can go on a zipped attachment (https://support.google.com/mail/answer/6590). I want to attach a small zip file (146.7 kB), which only contains the following extensions:
jpg, plus some text files without extension. There's no zip file inside the zip file. It seems I'm following their rules.
So why do I keep getting a "safety reasons" block?
Some details: the file was created by "zip" application Zip 3.0 (July 5th 2008), by Info-ZIP running in Ubuntu 14.04. The command line was:
sudo zip pl20151214.zip * icon/* ../../includes_pl/*
Looks like there are some problems regarding the ../../ path. I can't exclude it using Archive Manager 126.96.36.199 for GNOME. But recreating the zip without this path the problem is solved.