In such a case, the free email service will already scan the file for viruses. Ie. hotmail, yahoo mail, gmail. Anyone sending me attachments I would direct them to email me at those addresses.
My email service is using gmail as the backend. So getting infected attachments are pretty low.
But if I DO happen to get such an attachment that is infected, last resort would be to scan it with 1 of the free online scanners.
I haven't gotten a virus for over 10 years now. No thanks to my anti-virus, but to my safe browsing and computing. Your regular computing habits will have to change when you are not using an anti-virus.