Gmail supports SMTP of alternative addresses

With this, you can send emails with your own SMTP server instead of Google's. This is especially useful for   professional addresses (of universities, companies, etc.). The recipient of your message will not be able to identify whether your message is sent from Gmail, an email client, or the standard webmail interface provided by your institution.

After some investigation, I have found the SMTP server (as well as the POP and IMAP ones) of HKBU to be net16.hkbu.edu.hk, and the SMTP port code 587.