Yes, GlockApps supports the testing mode via one dedicated email address.
To use the mode via one dedicated address, you need to create a sending account with your SMTP settings in GlockApps, get the proxy address and send the message to the proxy address. GlockApps will do the rest for you: create a test and re-send the message to the full seed list via your SMTP settings.
This mode eliminates the need to create a test manually and copy-paste the id in the message. Plus, it provides the ability to select the email addresses for the test individually, not by groups like in the manual email spam test.
Read more about email testing via one proxy email address.