Rated 5 out of 5 stars

by Miguel Dias on Aug. 18, 2026 ·

This standalone add-on appears to install and then immediately remove itself from Thunderbird 153.

This is by design. THIS ADD-ON is NOT for Thunderbird 153 and above.

The Thunderbird Pro add-on bundles Thundermail, Appointment, and Send together, and as of Thunderbird 153, all three are now built directly into Thunderbird itself.