Controlled Location Setup
This setup often works in controlled locations (such as in China). It gets around many problems that individual Internet providers, or states, implement in order to restrict SMTP traffic.
Change your SMTP settings to the following:
SMTP server: port80.smtpcorp.com
Port: 443
And, turn SSL/TLS *on*.
You can also try the following:
SMTP server: smtpcorp.com
Port: 465 or 8465
And, turn SSL/TLS *on*.