To diagnose problems with Thunderbird, try one of the following:

• Restart Thunderbird with add-ons disabled (Thunderbird Safe Mode). On the Help menu, click on "Restart with Add-ons Disabled". If Thunderbird works like normal, there is an Add-on or Theme interfering with normal operations. You will need to re-enable add-ons one at a time until you locate the offender.
• Restart the operating system in safe mode with Networking. This loads only the very basics needed to start your computer while enabling an Internet connection. Click on your operating system for instructions on how to start in safe mode: Windows 10, Windows 8, Windows 7, Windows Vista, Windows XP, OSX

If safe mode for the operating system fixes the issue, there's other software in your computer that's causing problems. Possibilities include but not limited to: AV scanning, virus/malware, background downloads such as program updates.

"Everything in the migration works perfectly, except for "check for new messages at startup" is not working. No other problems except this. I already tried the whole list of simple and obvious things,"

Please skip over the "Your an idiot" solutions.

Is this possibly caused by the bug for POP accounts and Local Folders as the default account?

https://bugzilla.mozilla.org/show_bug.cgi?id=1584060#c55

No luck. Tried messing around with these settings, nothing seemed to work. I have defined 7 email accounts, plus local folders. Account 1 and 7 are set for read at startup.

user_pref("mail.account.account1.identities", "id1,id7"); user_pref("mail.account.account1.server", "server1"); user_pref("mail.account.account2.server", "server2"); user_pref("mail.account.account3.identities", "id2"); user_pref("mail.account.account3.server", "server3"); user_pref("mail.account.account4.identities", "id3"); user_pref("mail.account.account4.server", "server4"); user_pref("mail.account.account5.identities", "id4"); user_pref("mail.account.account5.server", "server5"); user_pref("mail.account.account6.identities", "id5"); user_pref("mail.account.account6.server", "server6"); user_pref("mail.account.account7.server", "server7"); user_pref("mail.account.account8.identities", "id6"); user_pref("mail.account.account8.server", "server8"); user_pref("mail.account.account9.identities", "id8"); user_pref("mail.account.account9.server", "server9"); user_pref("mail.account.lastKey", 9); user_pref("mail.accountmanager.accounts", "account1,account2,account3,account4,account5,account6,account7,account8,account9"); user_pref("mail.accountmanager.defaultaccount", "account1"); user_pref("mail.accountmanager.localfoldersserver", "server2");

bcowen said

"Everything in the migration works perfectly, except for "check for new messages at startup" is not working. No other problems except this. I already tried the whole list of simple and obvious things," Please skip over the "Your an idiot" solutions.

Those are not the "your an idiot" solutions. They are the best practice approach to diagnosis. My guess is the issue will be related to your security suite, but I have no basis for that, just a long experience with bad software from security vendors.

It is also a really good idea to eliminate these two things before launching into hidden prefs addons and anti virus are both more than capable of making the symptoms the same as 1584861.

The main discussion is occurring in https://bugzilla.mozilla.org/show_bug.cgi?id=1584861 and the software fix appears to be in https://bugzilla.mozilla.org/show_bug.cgi?id=880602

But I will leave you with sfhowes.

I solved the problem and other problems that popped up. It was a corrupted file in the Thunderbird profiles folder:

session.json

Just deleted this file and all the weird problems I was having with Thunderbird were fixed.

Just to note: Not every problem is caused by AV suite, fire walls, Safe mode, or other "Your an idiot" knee jerk solutions to tech problems. By the time someone posts a question, they have likely tried all the basic self help solutions. By fully reading a question before giving a knee jerk response, this can be quickly determined, and solutions to problems can be narrowed down a lot quicker.

bcowen said

By the time someone posts a question, they have likely tried all the basic self help solutions.

Two things. 1. You assume far to much. Most people have seen something they do not like or received an error message before they post, nothing more. Many have not even read any of the support articles or similar. They are frocused on their minute with the support rep. This is particularly so for those from the US who waste time posting that they want a phone number to "talk to someone"

2.

just migrated from a Windows 7 PC to a Windows 10 PC. Everything in the migration works perfectly, except for "check for new messages at startup" is not working. No other problems except this. I already tried the whole list of simple and obvious things, including searches for similar problems.

What steps do you think the folks in support should assume you have taken? We know exactly what you tell us, and in this case you told us nothing about what you had done beyond generalities.

3.

I solved the problem and other problems that popped up.

In the interests of full disclosure, perhaps you might have mentioned what they were,

I am please you found a solution, but you have actually been your own worst enemy here by failing to fully disclose what the issues were and failing to spend the time elucidating on what you had already done. SO before you post about people not fully reading, perhaps consider what you actually supplied. Almost nothing.

So how did you end up with a damaged session.json file anyway. It was working on one device, you copied it to another and is was corrupt. So what corrupted it? Was Thunderbird open when you copied it? That is the only reason I could see it would normally occur. Especially if we do not consider other software running on your machine.