More likely our update is one version ahead of what your anti virus is programmed to accept.

Disable email scanning and check the files wall is set to accept the current version.

Not the answer I'm afraid. It still doesn't work. Antivirus off, all Thunderbird allowed and trusted in firewall. The firewall doesn't seem to be version-specific - just Thunderbird, but it is all enabled to work.

What anti virus? Please add the troubleshooting information to your post To find the Troubleshooting information:

• Open Help (or click on three-line-icon and select Help)
• Choose Troubleshooting Information
• Use the button Copy to clipboard to select all. Do not check box "Include account names"!
• Paste this in your post.

The antivirus is Panda and the firewall is Zonealarm. but these were both disabled to test. It looks like it is both SMTP and IMAP that are dead so Thunderbird is totally screwed. One of the errors is saying that the connection is being actively refused which points to an authentication issue. The settings look as they should so this update has done something to corrupt my settings by the look of it. Here is the log:

 Application Basics

   Name: Thunderbird
   Version: 38.6.0
   User Agent: Mozilla/5.0 (Windows NT 10.0; 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, , (imap) imap.yandex.com:993, SSL, passwordCleartext
     OUTGOING: smtp.yandex.com:465, SSL, passwordCleartext, true

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

   account3:
     INCOMING: account3, , (imap) imap.mail.yahoo.com:993, SSL, passwordCleartext
     OUTGOING: smtp.mail.yahoo.com:465, SSL, passwordCleartext, true

 Crash Reports

 Extensions
   Lightning, 4.0.6, 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.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
     gfx.direct2d.disabled: false
     gfx.direct3d.last_used_feature_level_idx: 0
     layers.acceleration.disabled: false
     mail.openMessageBehavior.version: 1
     mail.winsearch.firstRunDone: true
     mailnews.database.global.datastore.id: 219fade9-133a-4cc2-a614-38f7f4b9a72
     mailnews.database.global.views.conversation.columns: {"threadCol":{"visible":true,"ordinal":"1"},"flaggedCol":{"visible":true,"ordinal":"3"},"attachmentCol":{"visible":false…
     network.cookie.cookieBehavior: 2
     network.cookie.prefsMigrated: true
     network.predictor.cleaned-up: true
     places.database.lastMaintenance: 1455427839
     places.history.expiration.transient_current_max_pages: 104858
     plugin.importedState: true
     privacy.donottrackheader.enabled: true

 Graphics

     Adapter Description: NVIDIA GeForce GTX 660
     Vendor ID: 0x10de
     Device ID: 0x11c0
     Adapter RAM: 2048
     Adapter Drivers: nvd3dumx,nvwgf2umx,nvwgf2umx,nvwgf2umx nvd3dum,nvwgf2um,nvwgf2um,nvwgf2um
     Driver Version: 10.18.13.6175
     Driver Date: 1-22-2016
     Adapter Description (GPU #2): Intel(R) HD Graphics 4600
     Vendor ID (GPU #2): 0x8086
     Device ID (GPU #2): 0x0412
     Adapter RAM (GPU #2): Unknown
     Adapter Drivers (GPU #2): igdumdim64 igd10iumd64 igd10iumd64 igd12umd64 igdumdim32 igd10iumd32 igd10iumd32 igd12umd32
     Driver Version (GPU #2): 10.18.15.4256
     Driver Date (GPU #2): 7-17-2015
     Direct2D Enabled: true
     DirectWrite Enabled: true (10.0.10586.0)
     ClearType Parameters: ClearType parameters not found
     WebGL Renderer: false
     GPU Accelerated Windows: 1/1 Direct3D 11

     AzureCanvasBackend: direct2d 1.1
     AzureSkiaAccelerated: 0
     AzureFallbackCanvasBackend: cairo
     AzureContentBackend: direct2d 1.1

 JavaScript

 Incremental GC: 1

 Accessibility

   Activated: 0
   Prevent Accessibility: 0

 Library Versions

     Expected minimum version
     Version in use

     NSPR
     4.10.10
     4.10.10

     NSS
     3.19.2.2 Basic ECC
     3.19.2.2 Basic ECC

     NSS Util
     3.19.2.2
     3.19.2.2

     NSS SSL
     3.19.2.2 Basic ECC
     3.19.2.2 Basic ECC

     NSS S/MIME
     3.19.2.2 Basic ECC
     3.19.2.2 Basic ECC

It's all gone very quiet. Thunderbird is completely non-functional. I have tried 2 other older versions and they are the same. When I go to set up a new account I get an error "Sorry, we're unable to communicate with our sign-up server" (which I don't use). I then enter my (correct) details for my email account, check the servers are correct, leave it on auto-detect and I get the error "Thunderbird failed to find the settings for your account". I then specify the ports and SSL/TLS (same as I use in Outlook which all works). When this doesn't work I try every possible permutation but it never works. This all points to a firewall problem but I don' t use Windows Firewall (it is disabled) and Zone Alarm is disabled. I'm stumped....

It is so hard with Windows 10. Basically the next step is boot windows into safe mode with networking and see if it works at that point.

Basically follow the instructions here http://www.digitalcitizen.life/4-ways-boot-safe-mode-windows-10

Use the 2. style to get to the actual safe mode with networking menu.

Does it work in that mode?

Thanks Matt. I tried your suggestion, guessing it probably wouldn't work, and sure enough, no change. It doesn't strike me as being a driver or network issue. Why do Microsoft keep making it more difficult for techies to fix things? F8 used to be simple.... (no answer to that of course). I've had Windows 10 on for about 6 months, purely because I need to learn it to fix other peoples' computers but I would like to go back to 8.1 which I preferred, in spite of what the "experts" say. I have disabled every bit of spying possible and had I not been able to do that would have stuck with 8.1 or preferably moved to Linux, which will be my next upgrade. I've had enough of Microsoft! Anyway, all I know is my Outlook runs 2 mail accounts perfectly so does another email program I put on for testing, and Thunderbird doesn't work with identical settings, firewall and antivirus disabled. It simply can't see any servers. I have changed every setting available out of frustration but to no avail. It worked before the upgrade but not after and now no version of Thunderbird works. I used Revo to uninstall which takes everything out for a clean reinstall but that has done nothing. Thunderbird works on my Linux machine quite happily so it is specific to my main PC. I think I'll just use the new program I downloaded which is a shame after using Thunderbird for many years. Thanks again for trying.

I assume you have checked the firewall Someone on here mentioned yesterday that that was their issue..

When you say checked, what do you mean, outside of disabling it which I have already done many times (first thing I looked at). It does. as I said earlier, point to it being a firewall but then it should work when I take it out. Zone Alarm only deals with allowing, or denying the executable (the way I have it set up), it is not version specific even though it may know that there is a different version installed by structure, I'm not sure entirely how it works. Given that I have completely uninstalled Thunderbird, cleared all rules in the firewall, reinstalled Thunderbird and re-checked the new rules just to be sure and then disabled it after verifying it still does not connect to any servers I'm back to being stumped.

I note you said you had disabled ZoneAlarm Firewall, but maybe Windows 10 auto enables the Windows Firewall in this situation.

What version of ZoneAlarm are you running? Have you tried to uninstall ZoneAlarm and then install a fresh up to date version and then make sure Thunderbird is allowed?

No, I checked that as well. Windows firewall is still disabled and I don't think as a rule it has the capability of switching itself back on if it detects there is no other firewall. I have it off in Services. I know Microsoft has a habit of turning things back on that I turn off so I always check everything. I have the very latest version of Zone Alarm on, only done last week and as mentioned previously have checked Thunderbird permissions. So, I have some more information. The reason I blamed Thunderbird was the blockage happened immediately following the last update. Outlook still worked with the same settings and so did one other mail program. I took this program off and tried 3 different alternative mail programs in a row and none of them worked at all. Only Outlook works and no other mail program will with identical settings, with all firewalls disabled. The error messages have changed from what they were in the beginning and are all now coming up with much the same thing and it's all to do with access permissions - I am being rejected (story of my life). Neither IMAP or SMTP servers on each account is accepting my login details (the same ones I use in Outlook so I know they are correct) on any program but Outlook and no firewall is blocking them. I should have mentioned I also use a hardware firewall but have physically removed that to test. I have never, in my long computer career. encountered this problem so cannot figure it out. I wonder if Microsoft is being naughty with me for blocking all their spying? I don't even trust their updates and have blocked them as well. I don't subscribe to the view that all updates are good for you, especially as Microsoft now enforces updates, except on my PC.