I'm sorry to hear about the trouble you are having with your email!
If you are trying to send messages via Canvas, this would be through the Inbox, which is separate to your School Email.
Our guide for How do I use the Inbox as a student? will walk you through this feature. Our guide for How do I send a message to a user in a course in the Inbox as a student? will walk you through this process.
If you aren't receiving notifications from Canvas, you will want to make sure those have been set up correctly. Our guide for How do I manage my Canvas notification settings as a student? will walk you through this process.
Please let us know if you have any other questions or concerns!