1. Is this happening with every e-mail address you have in Thunderbird?

2. Are all the malfunctioning ones using the same SMTP server in the Thunderbird settings?

Please answer these questions, and also please post here your Thunderbird Troubleshooting Information.

At the top right of the Thunderbird window, click the menu button (or use the regular menu at the top), then select Help: Troubleshooting Information.

Click the "Copy text to clipboard" button.  Do not check the box "Include account names"  Then paste (Ctrl-V), the text into your response here. We only need to see the sections down to and including the "Extensions" section, so you can delete the rest.

1. Is this happening with every e-mail address you have in Thunderbird?

Yes.. Having the same problem with other domain servers too. Also incoming emails are not getting delivered to my inbox. Till yesterday it was all fine. I reinstalled thunderbird (version 52.1.0) , but still having the same issues.

2. Are all the malfunctioning ones using the same SMTP server in the Thunderbird settings?

No.. there are three different ones.

Application Basics

   Name: Thunderbird
   Version: 53.0
   User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.11; rv:53.0) Gecko/20100101 Thunderbird/53.0
   Profile Folder: Show in Finder
   Application Build ID: 20170417145658
   Enabled Plugins: about:plugins
   Build Configuration: about:buildconfig
   Memory Use: about:memory
   Profiles: about:profiles

 Mail and News Accounts
   account1:
     INCOMING: account1, , (pop3) pop3.simplyblack.ca:110, alwaysSTARTTLS, passwordCleartext
     OUTGOING: , smtp.simplyblack.ca:587, alwaysSTARTTLS, passwordCleartext, true

   account2:
     INCOMING: account2, , (none) Local Folders, plain, passwordCleartext

 Crash Reports
   https://crash-stats.mozilla.com/report/index/bp-76bf30c8-3fe9-49c8-b3b3-50c3c2170302 (2017-03-02)

 Extensions
   Lightning, 5.5b2, true, {e2fda1a4-762b-4020-b5ad-a41df1933103}

 Important Modified Preferences

   Name: Value

     browser.cache.disk.capacity: 358400
     browser.cache.disk.filesystem_reported: 1
     browser.cache.disk.smart_size_cached_value: 358400
     browser.cache.disk.smart_size.first_run: false
     browser.cache.disk.smart_size.use_old_max: false
     extensions.lastAppVersion: 53.0
     font.internaluseonly.changed: true
     mail.openMessageBehavior.version: 1
     mail.spotlight.firstRunDone: true
     mailnews.database.global.datastore.id: a66af329-5dfa-d746-8c3c-3878500effa
     mailnews.database.global.views.conversation.columns: {"threadCol":{"visible":true,"ordinal":"1"},"flaggedCol":{"visible":true,"ordinal":"3"},"attachmentCol":{"visible":false…
     media.gmp.storage.version.observed: 1
     network.cookie.prefsMigrated: true
     network.predictor.cleaned-up: true
     places.database.lastMaintenance: 1494158820
     places.history.expiration.transient_current_max_pages: 122334
     plugin.importedState: true
     security.disable_button.openCertManager: false
     security.disable_button.openDeviceManager: false
     security.sandbox.content.tempDirSuffix: {c9963eba-a97d-f34f-881f-ccdf17a32ac2}

 Graphics

     GPU #1
     Vendor ID: 0x8086
     Device ID: 0x0d26

     Features
     WebGL Renderer: Intel Inc. -- Intel Iris Pro OpenGL Engine -- 2.1 INTEL-10.14.73

     AzureCanvasBackend: skia
     AzureFallbackCanvasBackend: none
     AzureContentBackend: skia
     AzureCanvasAccelerated: 0
     TileHeight: 1024
     TileWidth: 1024

 JavaScript

 Incremental GC: 1

 Accessibility

   Activated: 0
   Prevent Accessibility: 0

 Library Versions

     Expected minimum version
     Version in use

     NSPR
     4.13.1
     4.13.1

     NSS
     3.29.5
     3.29.5

     NSS Util
     3.29.5
     3.29.5

     NSS SSL
     3.29.5
     3.29.5

     NSS S/MIME
     3.29.5
     3.29.5

You only have one e-mail account set up in Thunderbird, not three. It is set up as POP, without SSL.

The standard POP port of 110 is often/usually blocked by Internet Service Providers (ISP).

I recommend that you switch to using IMAP, and use SSL. You will have to ask whoever is administering your domain hosting for the details of the IMAP server, and port number.

Read Switch from POP to IMAP account, for how to make the switch in Thunderbird.

I deleted the others.. and was trying to set it up again. but it wouldnt let me. I tried both. IMAP as well as POP. have the settings but its still not working.

I uninstalled and reinstalled Thunderbird several times. Still gives me the same message. I have given up on thunderbird now.

Using Macbookpro Mail client.

I deleted all email accounts. and now when I try making it again, any of them, I get a message unable to create account. 'error creating account. incoming server already exists' or username password invalid.

Its same for any other email account I am trying to create.

Is there anyway to Hard reset Thunderbird? is that even possible?

I have gotten used to using thunderbird. Been using it for past 7-8 years.

This is another error message i get.

[Exception... "Component returned failure code: 0x80004005 (NS_ERROR_FAILURE) [nsIMsgAccountManager.createIncomingServer]" nsresult: "0x80004005 (NS_ERROR_FAILURE)" location: "JS frame :: chrome://messenger/content/accountcreation/verifyConfig.js :: verifyConfig :: line 60" data: no]

How about repeating the troubleshooting information.

Also check you have no remaining outgoing servers in outgoing servers (SMTP) in account settings. Deleting an incoming mail account does not remove the outgoing server and associated credentials.

Strange as it may appear to you. the original developers never envisaged a time when folk would routinely delete their data it an attempt to fix a problem instead of correcting the relevant issues with the settings.

Do you have any form of anti virus or a proxy?

When I check I find an SSL server mismatch caused by the domain host trying to save money and sell sub standards products. See here

I suggest you read carefully and information they supply on creating exceptions for connecting to their server using SSL. Or simply do not use SSL.

This report indicates the mail service offered on the server is not standards compliant. But that has never bothered tucows in the past.

Thank you Matt and Bruce for your replies.

I am a creative person, so have limited tech experience. I saw the links about SSL and DNS, but not much made sense to me. Is there anything I can do about this mismatch? I would like to take it up with hosting company. I have been with them for the past 5 years. Have three domains + hosting packages with them. I dont have any anti virus. I believe for mac there is non available.

Here is what I did... I deleted Thunderbird. and imported mailboxes to Mail (mail client for macbookpro). And then deleted thunderbird folder with the profiles. Re-installed thunderbird. Re-created the same accounts. And now for some reason unbeknownst to me.. they all working just fine!!

Like I said, I am not a technical person, but a good troubleshooter I guess. I just keep at it till somehow I am able to resolve the issue.

Thanks again for all your help!!

I was going to say to create a new Thunderbird Profile to try to solve the issues. You beat me to it.

Glad to hear that you have it working properly now.

FYI: When someone says they are giving up on Thunderbird and are using another e-mail program, that's the point I usually stop paying attention to them.

Bruce A. Johnson said

I was going to say to create a new Thunderbird Profile to try to solve the issues. You beat me to it. Glad to hear that you have it working properly now. FYI: When someone says they are giving up on Thunderbird and are using another e-mail program, that's the point I usually stop paying attention to them.

I did give up on Thunderbird... but then have gotten so used to it, that decided to roll up my sleeves and give another shot.. once it kept saying that 'this server already exists' I figured there has to be a way to hardset the delete. But before that I needed to save some emails. Which I managed too! Imported the mailboxes to Mail Client! (gloating over my tech skills :-))

Thanks again, for spending so much time with me. Cheers!

> decided to roll up my sleeves and give another shot.. once it kept saying that 'this server already exists' I figured there has to be a way to hardset the delete. But before that I needed to save some emails. Which I managed too! Imported the mailboxes to Mail Client! (gloating over my tech skills :-))

nice work!!

And you are still running without any problems??