Clicking an email address on a website can launch a different composer from the mail application you normally open yourself. Firefox’s mailto action controls that route. The application selected by the browser and the account selected inside that application both need checking.

Identify the entry point

Use a trusted page containing a harmless email link, then observe what opens. Do not send the resulting message. Note whether Firefox opens a webmail tab, starts a desktop application or asks which program to use.

Open Firefox Settings and locate its Applications or Files and applications section. Find the mailto content type and inspect its Action. Mozilla documents choices including Always ask, the operating system’s default mail program, a listed webmail service and another installed application. The settings panel’s location varies between Firefox versions.

Record the old action before changing it. Choose Always ask if you deliberately use more than one mail workflow, or select the intended supported service. This browser choice need not alter every email link opened from other applications on the computer.

Test the composer without sending

Return to the same link and open it again. Inspect the recipient, subject and any prefilled message text, then check the From account. A correct Gmail or Outlook window can still be signed into the wrong identity.

If the From identity is wrong, correct the account within the mail service or use the appropriate browser profile; changing mailto again will not necessarily select another mailbox. Close the test composer and discard the harmless draft when finished.

If a required action is missing, record the Firefox version and available choices for support. Mozilla describes Refresh as a way to restore default content-type actions, but it also resets other customisations. Do not jump to that broad change before establishing the missing handler and preserving relevant settings. Completion means the link opens the intended composer with a verified identity, not that a test email has been sent.

Sources: Mozilla Support.