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Thunderbird 140.0.1esr (64-bit) Causing High CPU Usage and Overheating on macOS Catalina

BlengBlong
Making moves

Hi everyone,

I recently updated Thunderbird to version 140.0.1esr (64-bit) on my MacBook Pro running macOS Catalina, and I've encountered a serious performance issue since the update.

Issue Summary:

  • After launching Thunderbird, my MacBook's fans ramp up aggressively, and the CPU temperature spikes to nearly 100°C.
  • According to Activity Monitor, Thunderbird is consistently using around 60% of CPU resources, even when idle.
  • This behavior was not present in the previous version—Thunderbird used minimal CPU and ran quietly.

🧪 Troubleshooting Steps Taken:

  • Restarted the system and relaunched Thunderbird — issue persists.
  • Disabled unnecessary add-ons and extensions — no improvement.
  • Checked for background indexing or sync activity — nothing unusual.
  • Verified that no other apps are contributing to the spike — Thunderbird is the sole culprit.

📌 System Details:

  • macOS Catalina 10.15.x
  • MacBook Pro (15-inch, Mid 2012)
  • Thunderbird 140.0.1esr (64-bit)

Has anyone else experienced similar overheating or CPU spikes after this update? I'd appreciate any insights, workarounds, or confirmation from others facing the same issue.

Thanks in advance!

8 REPLIES 8

siffemcon
Contributor

Lots of troubleshooting steps here. 

aasawchuk
Making moves

I noticed exactly the same behavior on my MacBook Pro (16-inch, 2019) running Catalina 10.15.7 and Thunderbird 140.0.1esr .  The fans run continuously.  Thunderbird uses 5% of CPU with nothing else but Finder active.

Did you try any of the troubleshooting steps I mentioned above?

I completely solved the problem by going back and re-installing Thunderbird 128.11.1esr on my MacBook Pro running Catalina 10.15.7.  No more overheating, no more continuous fan running.  Thunderbird 140.0.1esr needs a fix.

andreamoretti
Making moves

Hi everybody,
I have almost the same exact problem: MacBookPro9,2, Catalina 10.15.x, Thunderbird 140.2.0esr.
Almost because I have a difference: I always have two processes of Thunderbird running when Thunderbird is open, and the sum of CPU usage is always minimum 100%.

Thank you for the help

Andrea Moretti

siffemcon
Contributor

The bug that causes this has been fixed but will take some time to appear on release versions.

wsm
Thunderbird Team
Thunderbird Team

I believe the issue with Catalina versions has been resolved in ESR version 140, currently 140.3.1.  Let us know if is not.

Please in the future use https://support.mozilla.org/en-US/questions/thunderbird for support and problem issues.  Thanks.

Yes, I confirm.

Thank you!