How to Fix Mozilla Thunderbird not Starting?

Causes of Thunderbird Not Responding

If Thunderbird refuses to start and returns an error about an existing Thunderbird process, it’s because Thunderbird thinks your profile is in use. The cause might be a stale profile lock that was left after Thunderbird crashed. This means Thunderbird didn’t close properly or correctly clean up temporary files. Additional processes are running in the background and Thunderbird is confused, frozen, and unable to open.

Another cause might be that Thunderbird is running on another computer. Thunderbird can’t run on more than one computer at the same time with the same profile.

How to Make Thunderbird Start Again

If Thunderbird is running but not responding, or it’s saying that your profile is in use, here are the steps you should try.

  1. Close and reopen Thunderbird. It’s always worth a try to close the application and then reopen it. Select Thunderbird > Quit Thunderbird from the menu, and then reopen the application to see if this solves the problem.
  2. Close Thunderbird on another computer. If Thunderbird is running with your profile on another computer, close Thunderbird on that machine by selecting Thunderbird > Quit Thunderbird from the menu. Then log in again on the computer you’re using.
  3. Kill Thunderbird’s background processes. Even if you closed Thunderbird, the application might be running in the background. Ending Thunderbird processes that are running in the background might fix the issue. On a Windows system, do this from the Task Manager.
  4. Restart the computer. Restarting is an easy fix that often solves many technical issues.
  5. Start Thunderbird in Safe Mode. This starts the application without certain extensions or add-ons that caused the error message. Open in Safe Mode and see if this solves the problem.
  6. Delete the parentlock file. The parentlock file is created every time Thunderbird starts and should automatically clear after you close Thunderbird. If Thunderbird fails to complete the closing process properly, the parentlock file isn’t deleted. Manually delete the file to see if this solves the problem.
  7. Use the LockHunter file-unlocking tool. Use LockHunter to see what’s restricting Thunderbird from opening, and then shut down any holds on the program so that you can use it normally.
  8. Repair Thunderbird folders. A folder may be corrupted. Repair Thunderbird folders to see if this solves the problem.
  9. Create a new Thunderbird profile. There may be something wrong with your Thunderbird profile. Profiles in Thunderbird and Firefox store information about your settings, mail, accounts, and extensions you installed. If something goes wrong, back up your profile and then create a fresh one.
  10. Reinstall Thunderbird. If none of these troubleshooting steps solves the problem, move your profile folder to a different location to back it up. Then, reinstall Thunderbird without a profile present. Everything should start fresh.

How to Compact Folders in Thunderbird?

Over time, the file ruins the space in a significant amount, swelling and unnecessary. The only real solution for this is to create a new file without junk. It is called Compact folders in Thunderbird. People who use Outlook will be familiar with a signal to be compressed.

This is the same thing with a different name. When you delete or move e-mail from a folder, Thunderbird and other e-mail programs actually “hide” them, and these hidden E-Mail still live in the folder. Emptying the waste also does not remove them permanently.

These hidden e-mails remain in the folder until it becomes compact. If you do not compact folders, your mail folders can be very large. The program will also behave incorrectly, so it is a good idea to do this from time to time.

Do not confuse with compacting folders with compress file. This is not a unique feature of Thunderbird. The main difference is that by default most other email clients automatically compact the folder when some amount of space is wasted.

Compact Folders in Thunderbird

To compact all the folders in a single account:

Click on the account the left side and then click on “File >Compact Folders“. Depending on how much mail you have in compacting an account and how you have compacted the folders recently. it may take a few seconds or a few minutes. If you have a problem doing this and the process is trying to compact one folder at a time. click on the folder and select “Compact This Folder“.

Note: Try to avoid downloading e-mails while compacting the folder. It has been reported that it may cause corruption or “Folder is being processed” error.

For POP3 accounts: If offline support is installed, firstly go offline (“File > Offline> Work Offline”, or simply click on the icon that as look as a light bulb in the bottom left corner). For IMAP accounts: You can’t compact folders unless you are online.

Compact folders for IMAP accounts

For IMAP accounts, Thunderbird can automatically compact the inbox when you exit it. Go to “Tools > Account Settings > (Account Name) Server Settings” and exit on “Clear inbox”. If you check “Empty trash” at the exit time, then it will be empty and compact the Trash folder when Exit Thunderbird. You can also take help of Inbox IMAP setting for Mozilla Thunderbird.

How to convert Outlook .pst files to Thunderbird

Thunderbird can’t import a .pst or .ost file. Most import tools and Thunderbird require that a compatible version of Outlook be installed on PCs used to Convert Outlook .pst files to Thunderbird and To import messages from Outlook to Thunderbird, Outlook should be the default mail client. Mail import from Outlook works by using the Outlook program for email sources, not the built-in .pst file. Note that Thunderbird is a 32-bit program, so it can not be imported from the 64-bit version of Outlook.

Convert Outlook .pst files to Thunderbird

If you want to switch to Thunderbird and will no longer have access to Outlook, we will guide you through the process of transferring your .pst and .ost files to Thunderbird.

  1. Search your local .pst and .ost files

Outlook will store your .pst and .ost files anywhere in the App Data folder for Windows user: For example, look for Microsoft Office sites for locations of Outlook 2007, Outlook 2010, and Outlook 2013. You may have at least two mail files, both of which will need to be imported into Thunderbird. Whether it is in PST (outlook.pst, archive.pst) or Ost (outlook.ost) format, depending on which type of mail server and what Outlook you are using then, convert outlook .pst files to Thunderbird

  1. Convert your emails from .pst and .ost files to mbox

convert outlook .pst files to Thunderbird

  1. Find your Thunderbird “Local Folders”

Open the Mozilla Thunderbird, Right click on “Local Folders” then choose “Settings”. Now you will see “Local directory” for your “Account Settings”.

convert outlook .pst files to Thunderbird

Something like this,
C:\Users\%username%\AppData\Roaming\Thunderbird\Profiles\7l36jvtj.default\Mail\Local Folders
(You will have to allow “Show hidden files, folders, and drives)

  1. Copy mbox files into the Local Folders

Exit the Thunderbird and go to your “Local Folders” directory in an explorer and drag and drop your mbox files in that destination.

  1. Browse mbox

Restart Thunderbird, and you can see the mailbox in your Local Folders list.

Bad outgoing attachments Office 365 in Thunderbird

I have recent issues regarding Bad outgoing attachments Office 365 in Thunderbird. I always sent correct attachments with Thunderbird to mail client like Lotus Notes, or IBM Notes. Recently some workmates moved to Office 365 and, when I send them some attachments like pictures, they visualize badly because the original attachment arrives slightly bigger in size respect.

To the original: in some points of the original file is inserted in the byte ‘0xD’. If the same file is sent to Office 365 from Gmail, the attachment arrives identical. Reading some forums I tried to change some points of the Configuration Editor but no result is founded. Bad outgoing attachments Office 365 in Thunderbird.

Update Thunderbird settings for Office 365

1. Launch Thunderbird.
2. On the first launch, you may be prompted for your password for your email and
Click Cancel.

Bad outgoing attachments Office 365 in thunderbird

3. Mac Users: In Thunderbird, Click on Mail menu, It will show in the upper left corner, next
to the Apple icon.
Click the Account Settings

Windows Users: Click on the Thunderbird Menu button
Click Options then Account Settings.

Bad outgoing attachments Office 365 in thunderbird

4. For your email account, click Server Settings.

Bad outgoing attachments Office 365 in thunderbird

5. Under the Account Information tab, change the following settings:
a. Server Name:
b. User Name: Your full Primary email address,

Note: You can confirm your primary email address in the HMS White Pages.
6. Click OK

Bad outgoing attachments Office 365 in thunderbird

7. Click on the Outgoing mail Server and select your HMS outgoing mail server then, click Edit.

8. In the Settings window, change the following settings:
a. Server Name:
b. Port: 587
c. Connection security: STARTTLS
d. Authentication Method: Normal password
e. User Name: Your full Primary email address, usually in the form of
firstName and lastName. i. Log into
ii. Click on Preferences
iii. Then, Click  Messaging
iv. Your primary email address appears under the “E-Mail Options” heading

9. Click OK

10. Click OK again.

Bad outgoing attachments Office 365 in thunderbird
11. The first time you Send and Receive email, you will be asked to enter your HMS

Thunderbird is now configured to connect to the Office 365 email system.

How to add google calendar to Thunderbird’s lightning?

First, open the Thunderbird Tools menu (hamburger icon) and add-ons> Extensions. Check whether you still need to install the power or not download the add-on that you want, the extension of the cog icon Choose Install Add-ons from File. Browse to the download location, open the Add-ons installation file, and click Install Now. To complete the installation, you must restart Thunderbird for Add google calendar to Thunderbird lightning.

How to add google calendar to Thunderbird lightning?

With the lightning installed, you should see the lightning calendar icon at the top right, next to the task icon. Click the calendar icon to open the Lightning calendar tab.

How to add a calendar?

By default, you will see a Home Calendar in Lightning. To add a new calendar, right-click on the empty space below your current calendar and select New Calendar. You can choose on your computer or on the network.Please select the following to Add google calendar to Thunderbird lightning.

Add google calendar to Thunderbird lightning

Add a Private Google Calendar

Choose On the Network > Google Calendar to add your own Google Calendars and also Google Calendars shared with you.

Add google calendar to Thunderbird lightning

Note: The Google Calendar option is only available after installing the provider for Google Calendar. You can also now add public Google Calendar using the iCalendar format, which offers to read access only.

In the following window (you will see your calendar) you must provide Google E-mail address, sign in to your account, and Google Calendar will have to give the provider permission to manage your calendar or if you have done it earlier Are you an existing Google session? After logging into your Google account, you should see a list of your Google Calendar.

Add google calendar to Thunderbird lightning

Check the calendar what you want to add, click Next, wait for the online confirmation that Your calendar has been created, and click to Finish.

You should now see Lightning populated with your Google Calendar events.

Add google calendar to Thunderbird lightning

How to fix UID FETCH server error Thunderbird?

UID FETCH server error Thunderbird, this article explains how to use one account in Thunderbird and send mail to multiple accounts. Those other accounts should be present on the mail server, but not present in Thunderbird. This is not the same as a global inbox that hides the existence of accounts in the folder pane. other accounts are not really present in thunderbirds. It makes it simple how you manage your email in Thunderbird and check out new mail and gain them.

It depends on sending multiple email addresses while posting and keeping an account with an email provider, from time to time to automatically receive mail from a POP server and merge it into a webmail inbox. An alternative feature is that your account receives mail from all the accounts from that inbox that the feature is called Mail Entertainer in, in, By adding an external POP server account to an account in Yahoo. Adding a POP3 Account to Mail Plus and Windows Live Hotmail.

UID FETCH server error Thunderbird

UID FETCH server error Thunderbird

This article will use Gmail’s Mail Fetcher until a raw message sees the source (you do this want to use View > Message Source in Thunderbird. They can not tell you have sent messages from your Gmail account.

The main drawback to doing so (in addition to working in setting it up) is that the new mail from other accounts will not be seen quickly. Gmail’s Mail will check the new mail more quickly, though you will get new mail in those accounts more often.

Replace several accounts with one account Thunderbird

  1. Back up your profile using something like Mozbackup
  2. Sign up for a Gmail account if you do not already have one
  3. Open Gmail account in Thunderbird. This can be either a POP or IMAP account if you use a POP account, you can configure it as a global inbox if you only want to see the local folder in the folder pane
  4. Enter the email address and username with a password of other accounts. Tools -> Options -> Security -> Password -> Saved Passwords if needed
  5. Safe location, such as Local Folders, to move all folders to other accounts. You may find it easiest to create a child folder for each account. So that you can drag and drop existing ones without running against the naming. Otherwise, you will have to select all the messages in the folder and instead have to move it.

You can organize your saved messages later

  1. Compact folders in each folder by selecting an account in the folder pane, and then file -> Compact folders, except Gmail.
  2. Delete other accounts. You can delete it by selecting it in Tools > Account Settings, and then “Remove Account” from the “Account Actions” list box.
  3. Follow these instructions to make Gmail’s Mail Fun to tell you about the pop accounts you want to receive via email. If you want to change the existing IMAP account, check that your email provider also provides a POP server. You may enable POP access by using the browser to enter that email provider’s webmail.
  4. Add email addresses of deleted accounts in the Gmail account as additional identities. See multiple identities for that e-mail account, how to do that. Do not forget to register each email address on GmailWebmailSettings -> Accounts -> “Add another email address
  5. Your inbox will contain messages sent to several email addresses. If you want to make it easy to choose which message was sent to. Then use the account color add-on to highlight the mail using a different color for each identity (email address). Another way to do this would be to add a colorful tag. To add a message filter on which the message was sent. Or you can create a separate folder for each email address (call it to whichever you want) and use it.

To automatically transfer your message to a new filter.

  1. Support of multiple identities is sufficiently smart to default. To the email address in which the message was sent, upon reply. When you create a new message, select the email address you want to use from: from the drop-down list. If you create separate folders to store mail sent to each email address. You can use the identity (to address) instead of sending new mail. From each account to the folder account add-on Can be used.
  2. Combine your saved messages with deleted accounts.

If you are facing issues with UID FETCH server error Thunderbird, Contact Thunderbird expert for your solution.