You may have your email client configured with the wrong SMTP server for your Internet Service Provider (ISP):
When sending from your SOM email account on campus, you use the School of Medicine SMTP (outgoing mail) server to send mail. When sending email from home, you use your Internet Service Provider's SMTP server.
If you are using a laptop and use the same email program to read, receive and send mail from campus and home, you must change your SMTP server each time you change location of your laptop. You can configure your email client to switch SMTP servers by using a program called Autoroute SMTP.
You may have the wrong SMTP server for the School of Medicine:
Check your email client settings and ensure that you are using the correct SMTP server for the School of Medicine