If you are talking about printing web mail from Firefox, select that printer in the "native print dialog" box, which is what you see when you do File > Print or {Ctrl + P}. Firefox uses the last used printer as its default printer, so going forward that printer should stay as the default in Firefox.

the-edmeister - "should", but doesn't.

As posted before by sunk818 [http://support.mozilla.com/en-US/ques.../716839#answer-128876] :

"I have this problem too. The print I last selected doesn't stay changed either.

Here is what I've noticed:

1) If I change the printer after a pop-up screen brings up the print feature, the printer is not changed.

2) If I go to print a page (say the Google home page) via File Print and change the printer, the printer and settings are saved once I print a page.

This leads me to conclude that changing printer settings on a popup automated print screen does not save. "

That worked for me. Very hackish though. Needs to be addressed. Happens EVERY time I change to print a Gmail mail with PrimoPDF rather than my usual printer, then it gets stuck on PrimoPDF forever, unless I do what sunk818 said above.

EDIT: It also doesn't seem to change if you hit Ctrl-P on the print page from a Gmail mail. It has to be a webpage that was not opened via Gmail-Print.

I HAVE THE ANSWER. Go to Control Panel>Printers & Devices. Windows comes with icons for several printers you are not using, such as Quicken PDF. Right click each and remove them. Your email (or other program) will now default to, or stay selected to, the only remaining printer/your default printer.

"...Firefox uses the last used printer as its default printer."

This is a major design defect. For anyone who is a couch potato, this does not matter. But for anyone else, it's an incredibly poor default behavior. There should be a setting to turn this mode off and allow FireFox to always use the default System Printer instead. One of the features of Windows 7 is that it can be made "network aware" so that when, for example, you are at home, it recognizes that and automatically sets your home printer as the default printer, and when you take your laptop to work, it recognizes that network and automatically sets your office printer as the default printer. FireFox's behavior of "always default to the last printer used" is not just bad programming, it's incredibly annoying as it defeats this great OS feature.

@TyroneJ

File a Bug report about that issue.
https://bugzilla.mozilla.org/

https://quality.mozilla.org/docs/bugzilla/starter-kit/how-to-write-a-proper-bug/