Does what I need. About the only thing that could be better is dismissing the help text when I click the toolbar button.

Ok

You throw out terms that don't seem to have clear meanings. You tell me to "create" something, but I don't know what it is -- much less what one looks like. It's really horrible to pay to subscribe to something that doesn't give clear instructions, understandable examples, purpose, etc.

It's useful, but I could use a simpler means to get the mail address - it would be nice to have copy button upon clicking the icon - 2 clicks to have the address, instead of going to "Manage all masks" wait for it to load, sign in (I have no idea why it sing off) and then get it.

Good.

I've been testing the free Firefox Relay service for a while and I've just decided to take the premium subscription.
I find it very practical and useful.
However, a function to see which sites are used for each alias would be very useful in the future.