Incoming email with smime.p7s attachment
This is a scenario I have at work.
We're receiving emails with .p7s attached files from a single user of a company(hence the company domain for eg. abc.com) our users interact with via mail. We use IBM Lotus Notes for our email.
There are other users of the same domain who also send our users emails but in those emails we do not see a p7s file.
Also since we use a attachment filtration policy on our email gateway, the gw quarantines the email because of the file extension. The attachment filtration policy specifically contains p7s, p7m, pif, scr file formats, which were put there by some previous fella before. Which just raises another question about whether we should block this filetype at the email gateway?
Also we asked the same user to send us a simple plain text email for testing to our gmail accounts and the .p7s file wasn't attached to this email.
I read up on smime.p7s usage, but cannot understand why is it that only that one particular user's incoming email shows this file while others do not.
Also I guess I can just whitelist the .p7s extension and the emails won't be quarantined by the gw, would that be a security risk of some sort?
