You should talk to your network administrator or your ISP about message limitations. It depends on the email server configuration. We do not have enough information to give you a detailed answer. One thing to note though is that you may be permitted to send a large file but the receiving system may accept only smaller attachments (typically 10MB max). I would not send movies or other extremely large files by email. I would use other file transfer mechanisms like FTP or other file transfer sites.
Most exchange servers, as well as ISP’s actually cap this. For example, a 20MB file in one e-mail will not send, however, 5 e-mails with 5MB attachments will.
Hope this helps!