Email: Gmail: zip or not?

Self-tutoring about Gmail: to zip or not to zip?

I sent an email with an attached zip file to a friend, but they never received it. I tried again: still nothing. Next, I sent it to my old hotmail account. I received it there.

I wondered: is Gmail not accepting zip files as attachments? support.google.com/mail suggests that zip files can be blocked if they contain other types that are objectionable. .zip, itself, doesn’t appear in the list of forbidden extensions, which is meant to be updated often.

Next I contemplated the fact that my friend couldn’t receive the email with the zip attachment. Could, however, a Gmail message be composed to include a zip attachment, then sent elsewhere? I opened a Gmail, made a small zip file of my current resume, then attached that in a message from the Gmail account to my hotmail one. Success – with no complaints from Gmail.

Next, I decided to reply to that Gmail message (and therefore account) with a message carrying another zip attachment. Once again, it worked. I’ve got two emails in that Gmail account, one in Sent and one in Inbox, both with zip attachments.

What’s the story? Sometimes a zip file can be successfully attached to a Gmail message, then sent. Gmail, it seems, can track what’s inside the zip file: if the attached zip contains a forbidden other type of file, it may not work. Similarly, sometimes an email with a zip attachment can be received in Gmail, so long as Gmail doesn’t think the attached zip contains any forbidden file types.

In this case, the zips that did succeed were much smaller (around 300 KB) than the one that didn’t (around 5MB). Moreover, the successful ones carried only .docx and .pdfs, while the unsuccessful one contained a much greater variety of files.