I have checked with my email account provider, everything there is ok and my account settings are correct.

Can you post the account settings as per your email provider's instructions?

Also, can you post your Troubleshooting Information? At the top right of the Thunderbird window, click the menu button , then select Help > Troubleshooting Information. Press the Copy text to clipboard button and paste the information into your reply.

I've added the image (as an Uploaded Image) of the settings I confirmed with email account provider and here's the Troubleshooting Info minus about 30 lines of stuff re my 2nd printer which I took out because I got the message that the content of my reply was too long and I don't think my reply goes out until I get it below 10,000 characters. If you need those 30 lines or so, I'll send as a 2nd message.

 Application Basics

   Name: Thunderbird
   Version: 38.6.0
   User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0
   Profile Folder: Show Folder

             (Local drive)
   Application Build ID: 20160211132445
   Enabled Plugins: about:plugins
   Build Configuration: about:buildconfig
   Memory Use: about:memory

 Mail and News Accounts
   account1:
     INCOMING: account1, , (pop3) post.kos.net:110, plain, passwordCleartext
     OUTGOING: post.kos.net:25, plain, none, true

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

 Crash Reports

 Extensions
   Lightning, 4.0.5.2, true, {e2fda1a4-762b-4020-b5ad-a41df1933103}

 Important Modified Preferences

   Name: Value

     browser.cache.disk.capacity: 358400
     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: 38.6.0
     font.internaluseonly.changed: false
     font.name.monospace.el: Consolas
     font.name.monospace.tr: Consolas
     font.name.monospace.x-baltic: Consolas
     font.name.monospace.x-central-euro: 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.tr: Calibri
     font.name.sans-serif.x-baltic: Calibri
     font.name.sans-serif.x-central-euro: 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.tr: Cambria
     font.name.serif.x-baltic: Cambria
     font.name.serif.x-central-euro: 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.tr: 14
     font.size.fixed.x-baltic: 14
     font.size.fixed.x-central-euro: 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.tr: 17
     font.size.variable.x-baltic: 17
     font.size.variable.x-central-euro: 17
     font.size.variable.x-cyrillic: 17
     font.size.variable.x-unicode: 17
     font.size.variable.x-western: 30
     gfx.direct3d.last_used_feature_level_idx: 0
     mail.openMessageBehavior.version: 1
     mail.winsearch.firstRunDone: true
     mailnews.database.global.datastore.id: ee126308-104e-4f66-87c1-5703ed94223
     mailnews.database.global.views.conversation.columns: {"threadCol":{"visible":true,"ordinal":"1"},"flaggedCol":{"visible":true,"ordinal":"3"},"attachmentCol":{"visible":false…
     network.cookie.prefsMigrated: true
     network.predictor.cleaned-up: true
     places.database.lastMaintenance: 1455831860
     places.history.expiration.transient_current_max_pages: 104858
     places.history.expiration.transient_optimal_database_size: 167772160
     plugin.importedState: true
     print.printer_Brother_HL-2270DW_series.print_bgcolor: false
     print.printer_Brother_HL-2270DW_series.print_bgimages: false
     print.printer_Brother_HL-2270DW_series.print_colorspace:
     print.printer_Brother_HL-2270DW_series.print_command:
     print.printer_Brother_HL-2270DW_series.print_downloadfonts: false
     print.printer_Brother_HL-2270DW_series.print_duplex: 0
     print.printer_Brother_HL-2270DW_series.print_edge_bottom: 0
     print.printer_Brother_HL-2270DW_series.print_edge_left: 0
     print.printer_Brother_HL-2270DW_series.print_edge_right: 0
     print.printer_Brother_HL-2270DW_series.print_edge_top: 0
     print.printer_Brother_HL-2270DW_series.print_evenpages: true
     print.printer_Brother_HL-2270DW_series.print_footercenter:
     print.printer_Brother_HL-2270DW_series.print_footerleft: &PT
     print.printer_Brother_HL-2270DW_series.print_footerright: &D
     print.printer_Brother_HL-2270DW_series.print_headercenter:
     print.printer_Brother_HL-2270DW_series.print_headerleft: &T
     print.printer_Brother_HL-2270DW_series.print_headerright: &U
     print.printer_Brother_HL-2270DW_series.print_in_color: true
     print.printer_Brother_HL-2270DW_series.print_margin_bottom: 0.5
     print.printer_Brother_HL-2270DW_series.print_margin_left: 0.5
     print.printer_Brother_HL-2270DW_series.print_margin_right: 0.5
     print.printer_Brother_HL-2270DW_series.print_margin_top: 0.5
     print.printer_Brother_HL-2270DW_series.print_oddpages: true
     print.printer_Brother_HL-2270DW_series.print_orientation: 0
     print.printer_Brother_HL-2270DW_series.print_page_delay: 50
     print.printer_Brother_HL-2270DW_series.print_paper_data: 1
     print.printer_Brother_HL-2270DW_series.print_paper_height: 11.00
     print.printer_Brother_HL-2270DW_series.print_paper_name:
     print.printer_Brother_HL-2270DW_series.print_paper_size_type: 0
     print.printer_Brother_HL-2270DW_series.print_paper_size_unit: 0
     print.printer_Brother_HL-2270DW_series.print_paper_width: 8.50
     print.printer_Brother_HL-2270DW_series.print_plex_name:
     print.printer_Brother_HL-2270DW_series.print_resolution: 0
     print.printer_Brother_HL-2270DW_series.print_resolution_name:
     print.printer_Brother_HL-2270DW_series.print_reversed: false
     print.printer_Brother_HL-2270DW_series.print_scaling: 1.00
     print.printer_Brother_HL-2270DW_series.print_shrink_to_fit: true
     print.printer_Brother_HL-2270DW_series.print_to_file: false
     print.printer_Brother_HL-2270DW_series.print_unwriteable_margin_bottom: 0
     print.printer_Brother_HL-2270DW_series.print_unwriteable_margin_left: 0
     print.printer_Brother_HL-2270DW_series.print_unwriteable_margin_right: 0
     print.printer_Brother_HL-2270DW_series.print_unwriteable_margin_top: 0
    
 Graphics

     Adapter Description: Intel(R) HD Graphics
     Vendor ID: 0x8086
     Device ID: 0x0102
     Adapter RAM: Unknown
     Adapter Drivers: igdumd64 igd10umd64 igd10umd64 igdumd32 igd10umd32 igd10umd32
     Driver Version: 9.17.10.2932
     Driver Date: 12-12-2012
     Direct2D Enabled: false
     DirectWrite Enabled: false (6.2.9200.17568)
     ClearType Parameters: Gamma: 2200 Pixel Structure: B ClearType Level: 100 Enhanced Contrast: 400
     WebGL Renderer: false
     GPU Accelerated Windows: 0

     AzureCanvasBackend: skia
     AzureSkiaAccelerated: 0
     AzureFallbackCanvasBackend: cairo
     AzureContentBac

Nothing obviously amiss there. Are you confident that the username doesn't have to be your full email address?

Can you access your email via your provider's website?

Yes I can access my email via provider's website. Re: Are you confident that the username doesn't have to be your full email address? I changed my username to my full email address and tried to get my messages but no luck -- still gives the message that it's checking my inbox and after a minute or so, message is no new messages.

A couple of odd other things to report: 1) Earlier today, over 60 messages were downloaded to my inbox, but all were ones I'd received about 4 days earlier, none of my new messages from the past few days. 2) In one of the tests the email provider tried, he transferred all my messages out of my inbox (at the provider's end), and then sent me a new email, and it came through to my inbox!

Does any of this shed any light on the problem?

Are you keeping messages on the server? If so, why?

I leave them because I can't be bothered going on and clearing them out. The server does that automatically after so many days or after a certain % of space is used. Also, sometimes it's handy when I'm on the road to have them there to refer to/respond to.

I just tried: emptied my inbox on the server, sending an email to myself from Tbird, and ... it came through! That may be problem solved. I'll see if emails from elsewhere come through before I start to celebrate.

No celebration yet. Tbird only retrieves my emails when there are only emails with text only in the server inbox. I tried sending myself: - text + emoticon - This came through to my inbox But, - text + doc attachment - text + jpeg attachment - text + png attachment - forward of a text only email None of these came through and when any one of them was in my server inbox, even a text only email in the server inbox would not come through.

Any ideas about what's going on? How to fix it?

Try to start Windows in safe mode with networking enabled.

- Win7 http://windows.microsoft.com/en-US/windows7/Start-your-computer-in-safe-mode

Still in Windows safe mode, start Thunderbird in safe mode. - https://support.mozilla.org/en-US/kb/safe-mode

Does the problem go away?

No, problem is still there -- bottom left corner message says downloading but then "no messages," but there are 2 messages in the server inbox.

Update Some time in the last 3 hours when I was away from my pc, Tbird did end up downloading the 2 new messages (with more than just text) to my inbox. Right now I'm running a test to see how long it takes download 2 new messages from the server inbox. It didn't download them when I clicked on "Get Messages" at 1 minute and 7 minutes after they appeared in my server inbox. It's been about 35 mins so far with no download. All very strange. I hope someone can make sense of this.

There is an interval you can set how often Thunderbird retrieves mail from the server. If this is set too aggressive, the server may deny subsequent connection attempts. An interval of 15 min should be fine.

Yes, mine is set for 10 mins, where I've always had it. As for any more downloads after my wait period, there were none. And one more point from earlier, after leaving Safe Mode, my display looked like it was still partly stuck in safe more -- many colours not showing, most graphics (e.g., the Google one, just the Search box itself) not showing. Finally got it to display properly by changing my theme settings in "Personalization" to Windows 7 Basic -- in case anyone runs into the same problem. As for my TBird problem, it looks like I'll have to re-install it and hope that a fresh start solves the problem. So thanks to you (and Zenos) for your suggestions.

The problem with TBird originated around when my router malfunctioned so I plugged my internet connection directly into my pc and set the network setting for Home, and then Office to see if that made a difference. Neither helped my TBird problem. I've now replaced the router with a new one and lo and behold, Tbird downloaded all my messages -- back to normal. I noticed that the new router set the network connection to Public (vs. Home or Office) so I guess that was the problem -- TBird saw the receiving of emails beyond anything but plain text as insecure/risky so blocked the download. I wish I'd tried the Public setting earlier to prove the point but I'm not messing with it now, just happy to have the problem solved.