So Thunderbird hands the message to your providers server and your provider claims to have sent them. How do you figure this is a Thunderbird issue?Ask your provider where your messages are going. The provider's webmail site does not use their SMTP server so that comparison means you know your username and password and nothing else.

Thanks for your response! The reason I am looking into whether this could be a problem related to Thunderbird is that the problem didn't exist until I got a new computer running Windows 10 and decided to try Thunderbird because I really dislike the mail program included with W10. I wasn't having this problem using that program, and never had that problem with the mail client on my old computer. It just started happening when I began using Thunderbird. I have had many sessions with the ISP support people, with no solution. I'm just trying to find out what's going on and if there's something I can do to correct the situation. If you think it doesn't sound like it could be related to Thunderbird, that's at least another piece of the puzzle. Thanks again for your time!

Open a new write message. TYpe some content. click on 'Options' and select 'Delivery Staus notification' Send a test email to me at this email address: mail at anje dot co dot uk

note I do not usually use this email address for responses as I post everything in the forum, but as a test please try it.

Post message in this forum when you have sent it.

Thanks, Toad-Hall! I have sent an email message to the address as requested, and am notifying you that I did that.

You will be pleased to hear that I received your email: sending this as requested to test email problem. Many Thanks!!

It was sent using 'Plain text' format only. Do you usually compose and send using plain text ?

I'm trying to see if there is a spam score applied by various servers. Can you do a repeat of sending to these email addresses.

anjeyelf at btinternet dot com anjeyelf at gmail dot com

Thank you! Have sent email to the two additional addresses, subject line "Thunderbird test 2".

I have not consciously chosen to compose/send in 'Plain text'; in fact didn't know I was doing that.

Can you post the following.

In Thunderbird

• Help > Troubleshooting Information
• Do Not select to include account names
• Click on 'Copy text to clipboard'
• In this forum question, right click in a 'Post a Reply' text box and selct 'Paste'.

Can you please confirm that your mail account name is your full email address.

Below is troubleshooting info as requested, account names not included. Account name is not the same as full email address.

 Application Basics

   Name: Thunderbird
   Version: 52.8.0
   User Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0
   Profile Folder: Open Folder

             (Local drive)
   Application Build ID: 20180516145259
   Enabled Plugins: about:plugins
   Build Configuration: about:buildconfig
   Memory Use: about:memory
   Profiles: about:profiles

 Mail and News Accounts
   account1:
     INCOMING: account1, , (pop3)110, plain, passwordCleartext
     OUTGOING: , 587, plain, none, true

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

 Crash Reports

 Extensions
   Lightning, 5.4.8, true, {e2fda1a4-762b-4020-b5ad-a41df1933103}

 Important Modified Preferences

   Name: Value

     accessibility.lastLoadDate: 1517711449
     browser.cache.disk.capacity: 358400
     browser.cache.disk.filesystem_reported: 1
     extensions.lastAppVersion: 52.8.0
     font.internaluseonly.changed: true
     font.name.monospace.el: Consolas
     font.name.monospace.x-cyrillic: Consolas
     font.name.monospace.x-unicode: Consolas
     font.name.monospace.x-western: Consolas
     font.name.sans-serif.el: Calibri
     font.name.sans-serif.x-cyrillic: Calibri
     font.name.sans-serif.x-unicode: Calibri
     font.name.sans-serif.x-western: Calibri
     font.name.serif.el: Cambria
     font.name.serif.x-cyrillic: Cambria
     font.name.serif.x-unicode: Cambria
     font.name.serif.x-western: Cambria
     font.size.fixed.el: 14
     font.size.fixed.x-cyrillic: 14
     font.size.fixed.x-unicode: 14
     font.size.fixed.x-western: 14
     font.size.variable.el: 17
     font.size.variable.x-cyrillic: 17
     font.size.variable.x-unicode: 17
     font.size.variable.x-western: 17
     mail.openMessageBehavior.version: 1
     mail.winsearch.firstRunDone: true
     mailnews.database.global.datastore.id: f2fb6154-3548-4e8a-b40f-72246d8eb7b
     media.gmp.storage.version.observed: 1
     network.cookie.prefsMigrated: true
     network.predictor.cleaned-up: true
     places.database.lastMaintenance: 1528238741
     places.history.expiration.transient_current_max_pages: 122334
     security.sandbox.content.tempDirSuffix: {db124644-9e15-44bb-b7d6-7ea7890afccf}

 Graphics

     GPU #1
     Description: Intel(R) HD Graphics 630
     Vendor ID: 0x8086
     Device ID: 0x5912
     RAM: Unknown
     Drivers: igdumdim64 igd10iumd64 igd10iumd64 igd12umd64 igdumdim32 igd10iumd32 igd10iumd32 igd12umd32
     Driver Version: 22.20.16.4771
     Driver Date: 8-13-2017

     Features
     Direct2D: false
     DirectWrite: true (10.0.17134.1)
     WebGL Renderer: Google Inc. -- ANGLE (Intel(R) HD Graphics 630 Direct3D9Ex vs_3_0 ps_3_0) -- OpenGL ES 2.0 (ANGLE 2.1.0.2a250c8a0e15)

     AzureCanvasBackend: skia
     AzureCanvasAccelerated: 0
     AzureFallbackCanvasBackend: cairo
     AzureContentBackend: skia

 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
     3.28.6
     3.28.6

     NSS Util
     3.28.6
     3.28.6

     NSS SSL
     3.28.6
     3.28.6

     NSS S/MIME
     3.28.6
     3.28.6

You sent the emails to additional email addresses, but they were never received. I checked the webmail accounts to see if anything went into various spam etc folders, but no results. This sounds like the issue you are describing.

I notice the email which I did receive from you does not have any mention of SPF (or DKIM) in the headers. This could be an issue with eg: gmail https://support.google.com/mail/answer/81126?hl=en Authenticate your mail section on eg: SPF https://support.google.com/mail/answer/180707 Fix messages that aren't authenticated sections.

Please read info at this link on how to add SPF .

• https://cruzio.com/member-tools/support/add-spf-records-website-hosting/

re : OUTGOING: , 587, plain, none, true Read info here:

• https://cruzio.com/member-tools/support/using-secure-email-ssl/

Then try using the following: For Outgoing server.

• Connection Security: STARTTLS
• Authentication Method: Normal Password

Thanks again for all your time spent on this, Toad-Hall! It's really appreciated.

I will pursue your suggestions.

Toad-Hall, thanks again. Your suggestions were useful in getting me to explore some other avenues, and I seem to have come upon a solution.

If you have managed to get a solution, I would be interested to know what you did.

I'm puzzled, actually, but I think it's working now, though I may be speaking too soon. I had one successful sending to an address that consistently doesn't receive my emails, but haven't heard from subsequent tests.

As I was looking at the various links you sent me, I had the thought that it just couldn't be this complicated, since it works with Windows Mail. Then I remembered my wife also uses Thunderbird on her computer and has an email account with the same domain and ISP; early on in my attempts at solving this I had tried simply copying her server settings, since her email seemed to work, but I had no luck. I decided yesterday to first check and see if indeed I could send an email from her computer using that account, to an address I can't send to; that email went through fine. In studying her server settings, the only thing I could see that I hadn't tried (that was different than mine) was that her incoming server was set as IMAP; mine, I believe on recommendation of my ISP, was POP3.

So, I set up a new email account and elected IMAP as my incoming server, and let Thunderbird choose the port and security settings. I noticed that gave me security settings of STARTTLS and Normal Password, as you had suggested trying.

I'm hoping this has indeed solved the problem, but I expect it will take a few days to be certain.

I'm puzzled as to why this should work, and I'm not completely sure it has, but I did have that one successful sending, so something shifted.

Please remember that IMAP does not work in the same way as POP.

POP will download and save a copy in eg: Inbox. This folder does not synchronise with server, so emails are stored in Thunderbird and when you delete emails, they are not necessarilly deleted off server; it depends upon what settings you have chosen.

IMAP offers a virtual display of emails in subscribed folders which do synchronise with server, so in effect they are one and the same. When you delete from an imap folder it is deleted off the server as well. If you want to secure copies in Thunderbird and delete off server, then you need to keep a copy in 'Local Folders' mail account.

Thanks, again, for all your help. Actually, I do need to be able to keep copies of emails on my computer, so that is valuable information for me, and I was not very clear on the differences between IMAP and POP. I still don't understand why making that change might have effected my ability to send emails, but perhaps I don't need to know, as long as it works, which it seems to be doing now.

Info on synchronisation: https://support.mozilla.org/en-US/kb/imap-synchronization

Keeping a full copy in Thunderbird imap mail account means you will be able to read emails even if in offline mode, just like a pop account.

In your case, you have a website which is hosted by cruzio.com and they offer you the email address. But if you decide to change the company who hosts your webpage then you would need to point your imap mail account to look at a different server. This is where many people come unstuck and lose emails. Before changing anything, you would need to synchronise those imap folders to get a full up to date copy stored in thunderbird imap mail account. Then in offline mode to stop further synchronising on folders, you would need to get a copy into 'Local Folders' mail account. Once this is done and you have checked you can still read those copied emails, then you can change who hosts the website and point the imap mail account server settings to the new server. When you point to new server, it does not have any of your old emails, so all the folders will synchronise with an empty server and show what is on that server, hence the loss of emails.

Whilst this is nothing to do with the original question, as you are new to imap and have a hosted website, I'm giving you a heads up, just in case you decide to change who hosts your website.

Many thanks for your thoughtfulness, Toad-Hall! I am indeed considering changing website host at some point, and that will be an important consideration.