In the browser, go here ---> about:logins Or click on the menu and go to passwords.

sorry, but could you be a bit more explicit please? Whereabouts is, about:logins? Doesn't appear in Settings or Tools, and Passwords in Settings refers to logins to external web-sites, and how does it relate to Firefox prefilling online forms with the wrong email address for me? thanks

I think I may have found the solution but only time will tell if it's right. Go to : Settings / Privacy & Security - Addresses & More, click on right arrow and it brings up a list of what looks to be post addresses (but is truncated). Select each address in turn and Edit, This brings up a list that includes organisation, full postal address, and an email address. I found one of the email addresses contained the typo so by correcting it I hope to have resolved the problem, but it'll need time to cover all the functions that pre-fill the email address.

I think I may have found the solution but only time will tell if it's right. Go to : Settings / Privacy & Security - Addresses & More

That's not for login information. Here's your login info. see screenshot

thank you but my question was never about logins. It was for pre-fills, ie when purchasing online and postal address/phone number/email address are requested.

typo in saved email address in pre-fill

That's where email addresses are saved to autofill.

So the autofill in a form is wrong. see screenshot Gotcha. Issue resolved???

looks like we have differences in Firefox as mine doesn't have a Prefill option - my email addresses for prefill are as I described above, in Addresses and More - looks like this:-