My wife has Hotmail and asked me if a ZIP attachment is safe to download. I didn't know, actually, even though I felt 99% sure it was scanned automatically. However, I still don't know the official answer, despite spending a full hour searching web sites (including MS pages) for a description of MS's virus scanning policies for Outlook.com downloads. I could only find statements by MS that try to score points against Google by saying they don't scan your emails for data to sell to advertisers. Funny, though, I find nothing saying MS scans for viruses, especially within ZIP files and other archives. My search for an answer should not be so hard.

Can anybody advise on this?

The topic is difficult because MS uses Outlook as a name for their popular email application with Exchange server, so the search results are highly contaminated. If any out there does have an answer, it would help to provide an authoritative reference, as I am not fond of taking a stranger's word that my data is safe because they say so.

1 Answer 1


It appears they do, how effective it is... thats harder to say:

Outlook.com also blocks suspected viruses by way of a reputation-based system: Content from parties with a poor reputation (a hit-and-run spammer, for instance) will be blocked, but you can unblock attachments for people you trust. Some attachment types -- EXE files, for instance -- are blocked entirely, even for trusted senders.

Regardless, there are basic internet / email rules that should be followed. such as if you receive a downloadable item that you do not recognize the sender or do not trust the sender, do not open it.

  • 1
    Thanks for trying to help. I had actually already read that part you quoted, but it does not even claim the reputation is based upon virus detection! Further, IMO it actually implies that reputation is based on spam activity, not virus detection. DOES THIS NOT CONCERN ANY READERS? How many clueless Outlook users are forwarding virus-infected cute kitten videos to each other? I hope Outlook.com has robust virus protection, but I'm still not aware of ANY virus protection.
    – Roger Dodger
    May 4, 2013 at 23:53
  • Blocking suspicious activity is a fairly easy way to combat problem emails. Combine it with the power of the clients (AV / On demand scanning) is much easier for the servers than running it themselves. I imagine there are liability concerns too, if MS says they actively scan and a virus gets through then to some extent MS is liable. Even in Exchange the server only processes rules, it does not actively scan for malware, it block exe files, macros, external images, or what ever the admin wants to block.
    – AthomSfere
    May 5, 2013 at 0:03
  • AthomSfere - I don't think liability is a concern. Other freemail services do it. On the other hand, redundancy over client scanning is a pointless cost if nobody is even asking you if you run AV scans. Perhaps MS is simply ahead of the game on the business model. Why have massive server farms running AV services when the client will do it anyway? Hmm. I wonder if I've exposed a "dirty secret" to MS profitability and Steve Ballmer has already sent a hit squad to silence me. ;-)
    – Roger Dodger
    May 5, 2013 at 1:43
  • Actually, it appears that Outlook.com offers protection in that it blocks suspected content via a reputation-based system, but that it does not take the time to scan anything. This is how you could download an infected attachment from a trusted source. I'd agree with @RogerDodger in that it should concern Outlook.com users, since there are other free mail providers that will specifically scan attachments. Gmail and Yahoo both scan attachments (and can thus be used as a virus scanner, if you send yourself suspect files as attachments).
    – Bon Gart
    May 5, 2013 at 4:37

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.