I'm getting a 501 Syntax Error when I try to e-mail someone. They can send me mail. Note that there is little we can do on this end to resolve this type of problem. Instead, have someone at the other site investigate the problem and upgrade or replace the appropriate product. E-mail is not necessarily an appropriate means for transferring large files.
Many systems limit the size of incoming messages.
If your message was rejected because it's too large, don't just resend. Instead, explore an alternate means, such as ftp. Your mail client is configured to send e-mail using your jefferson.edu address. Your mail client is configured to use an SMTP server other than smtp.jefferson.edu . You're sending to someone in care of a jefferson.edu address or that person is forwarding their mail to a jefferson.edu address.