What versions of Thunderbird?

Define "slow" please in terms of numbers.

Version, see screen shot.

Startup time 12,96 seconds.

As comparison Mac mail starts in 3,26 seconds and MS Outlook starts in 5,05 seconds on the same Mac.

In a virtual win 11 machine on the same Mac I get a startup time of 4 seconds with the same version of Thunderbird.

Does the same happen when you start Thunderbird in "troubleshoot mode"? Hold down the Alt (Option) key and launch Thunderbird ...

> In a virtual win 11 machine on the same Mac I get a startup time of 4 seconds with the same version of Thunderbird.

Tried disabling Thunderbird's access to the Mac address book?

"troubleshoot mode" did not do it, maybe one second faster.

"Disabling Thunderbird's access to the Mac address book?" I'm not sure where one does that but I removed it from the Thunderbird address book and "PANG" I got a startup time around 3 seconds 😊 One could say it solved the problem but it created a new one. It's not a showstopper for me but it would be nice to have continued access to the Mac address book.

IIRC, the current workaround for this situation is set up the Mac AB so it syncs to the cloud, and then set up Thunderbird AB as carddav to the cloud. Haven't tried it myself yet.

After activating iCloud start TB and open the Address Book tab. Click on the "Create a new address book" symbol and select "New CardDav Address Book" (image) Fill in your username (your Apple identifier) and as location type https://contacts.icloud.com/contacts/ (image)

Unfortunately I can't get it to connect. Via the web browser I can go to https://www.icloud.com/contacts/ but I can't make Thunderbird to connect!

After clicking on "Continue" in the second image you should see a new window asking for your password.... Did you activate iCloud and the two factor identification for your Apple account ? https://support.apple.com/en-us/102660