Hotmail, Yahoo, Gmail Attachment Size Limit

The figure given for Hotmail (and probably the others) is the total message size, not the individual attachments. The total message size is actually the sum of the sizes of all the attachments and images multiplied by about 1.34 (3 bytes of the image are encoded as 4 characters in MIME base64 encoding), plus say 4K for headers and body text (4K = 0.004MB). So a 5.1MB attachment plus another 2MB attachment would be too big for Hotmail. You will get a 552 error either from your email provider or the destination if you try to send something larger than the policy allows.

In general, I’d suggest not sending an email of greater than 1MB, certainly not if the recipient doesn’t expect it, as on narrowband connections it may take hours to download. People seem to forget that the purpose of email is to send information (primarily text with a few illustrative images) – you will often see emails containing something like an invitation (about 1K of information as text) with a logo that contains no information at all but wastes about 5MB. So it’s good if email users are conscious of this. (People used to be aware of such “netiquette” and not bottom-quoting until about 1999, but it doesn’t seem to be in most ISPs’ interests to educate newbies!)

There are times when you may want to send large high-resolution files to professional printers – generally FTP is best for this, and the printers may well provide an FTP upload instructions.