MIS limits the size of outgoing emails for our customers to 3.5 MB. (Hotmail will not accept emails larger than 2 megs)
If you are sending a very large email attachment to someone on another network, it is a good idea to compress the file to make it smaller (using a program such as WinZIP or Stuffit). The recipient you're sending to may not have enough storage space on their account to receive such a large file, so making the email smaller is a good precaution to ensure s/he can receive your email.
NOTE: when you send an binary file in email, it will be 33% larger than the original size, so if you send an attachment that is 1 meg in size, when it is turned into an attachment, it will be 1.33 megs in size.