(Note: you may need to generate an app password from your email service provider such as Gmail or Microsoft)
1. Double check your settings on Monitor->E-Mail tab. Here are some settings known to work using Gmail.
2. Verify that your local firewall and any antimalware/antivirus software you are running has exclusions for all the executables in the client install folder
3. Turn on verbose debug logging in the client using this FAQ.
4. Run a command prompt "As Administrator" and CD into the directory your software client is installed in and run the backup engine (it will be named with your brand and have a .EXE on end) with the -email command line option and you will see verbose output in the command window. For example, a successful email transmission looks something like the following in verbose mode: