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: mail.smtp2go.com
SMTP port: 443
And, turn SSL on.
If that doesn't work, try SMTP port: 465 or 8465
If all else fails, use a VPN service in conjunction with SMTP2GO.
A good guide for finding a reliable VPN: The best VPNs to use in China.