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I cannot install the Send Later add-on which schedules an email to be sent later.

When clicking on the send_later-9.0.11-tb.xpi file, I receive the following error in Firefox:

This add on could not be installed because it is not verified.

I tried opening about:config page, setting xpinstall.signatures.required and extensions.langpacks.signatures.required to false and restarting Firefox, according to this link, but it didn't work out.

Any suggestions on how to install this add-on?

(Ubuntu 22.04 LTS)

ljushu
  • 31

1 Answers1

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Solution: go to Tools > Add-ons and themes and add the Send Later add-on directly to Thunderbird.

ljushu
  • 31