This is allowed for two very specific purposes:
- Initial set up (or tear down, should it be necessary) of your MySQL database.
- Routine database administration tasks.
The best guideline for whether what you are doing is allowed is whether you are doing it. In other words, no automated port-forwarded access to MySQL is allowed; it must be you personally doing whatever you're doing. If, for example, you want to back up your process, you should use another method.
Because of the large variety of ssh clients and ssh-protocol tunneling applications that exist, and the innate complexity of ssh tunneling, we cannot provide any technical support related to remote access to your MySQL database.
To use ssh port forwarding in conjunction with the industry-standard OpenSSH client, one would use a command similar to the following on one's local system (not our ssh server):
YourPrompt> ssh -N -L 3306:your.db:3306 email@example.com
Please note that the command above needs significant specialization for use in your specific circumstances. If you are uncomfortable making the needed changes, this is not a feature you should attempt to use.