Sounds like it might be your anti-virus product causing this.

There is security software like Avast and Kaspersky and BitDefender and ESET that intercept secure connections and send their own certificate.

eg: BitDefender -> Privacy settings -> disable Scan SSL

Boot the computer in Windows Safe Mode with network support (press F8 on the boot screen) to see if that helps.

• http://www.bleepingcomputer.com/tutorials/how-to-start-windows-in-safe-mode/
• http://www.7tutorials.com/4-ways-boot-safe-mode-windows-10

Also some info here:

• https://support.mozilla.org/en-US/questions/1120453
• https://support.mozilla.org/en-US/questions/1056325

disabled my AV software and re tried, no change. ISP says it's a mozzilla software problem

Often disabling one anti-virus will only reset the default one on the computer. Did you Boot the computer in Windows 'Safe Mode with networking' and test to see if connection/download occured ?

safe mode with networking would not allow me to access the internet to try to download. I would add I have windows 10 if that makes a difference, also not extremely tech savy so I do thing cautiously

Are you sure about using port 110? It seems an unusual choice in a system that's reporting an SSL problem.

I see it suggests precisely pop3 and port 110 here: http://www.fairpoint.com/residential/support/emailsupport/#Thunderbird3 but it's a rather dated site, seeing as it talks about Thunderbird 2 and 3.

spent 30 min. with Fairpoint support trying to solve this, all settings are correct. It worked fine and then one day could only send e-mails thru TB not receive any. I like TB but guess I will have to try a new mail program

re: safe mode with networking would not allow me to access the internet Are you sure you did not select only 'Safe mode' because that would stop internet access.

Please post this info: In Thunderbird Help > Troubleshooting Information click on 'Copy text to clipboard'

In this forum question, right click in a 'Post a Reply' text box and select 'Paste' You can edit/remove all info on fonts and printers but nothing else.

Application Basics

   Name: Thunderbird
   Version: 45.2.0
   User Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.2.0
   Profile Folder: Show Folder

             (Local drive)
   Application Build ID: 20160630070546
   Enabled Plugins: about:plugins
   Build Configuration: about:buildconfig
   Memory Use: about:memory

 Mail and News Accounts
   account2:
     INCOMING: account2, , (none) Local Folders, plain, passwordCleartext

   account3:
     INCOMING: account3, , (pop3) mail.myfairpoint.net:110, alwaysSTARTTLS, passwordCleartext
     OUTGOING: , smtp.myfairpoint.net:587, alwaysSTARTTLS, passwordCleartext, true

 Crash Reports

 Extensions
   Lightning, 4.7.2, false, {e2fda1a4-762b-4020-b5ad-a41df1933103}
   McAfee Anti-Spam Thunderbird Extension, 2.0, false, msktbird@mcafee.com

 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
     dom.apps.reset-permissions: true
     extensions.lastAppVersion: 45.2.0
     
     mail.openMessageBehavior.version: 1
     mail.winsearch.firstRunDone: true
     mailnews.database.global.datastore.id: e4c97aa4-3c99-4637-ad9b-dce4802319c
     network.cookie.prefsMigrated: true
     network.predictor.cleaned-up: true
     places.database.lastMaintenance: 1473333123
     places.history.expiration.transient_current_max_pages: 104858
     plugin.importedState: true
     
   

 Graphics

     Adapter Description: Intel(R) HD Graphics 5500
     Vendor ID: 0x8086
     Device ID: 0x1616
     Adapter RAM: Unknown
     Adapter Drivers: igdumdim64 igd10iumd64 igd10iumd64 igd12umd64 igdumdim32 igd10iumd32 igd10iumd32 igd12umd32
     Driver Version: 20.19.15.4454
     Driver Date: 5-4-2016
     Direct2D Enabled: false
     DirectWrite Enabled: false (10.0.10586.494)
     ClearType Parameters: ClearType parameters not found
     WebGL Renderer: Google Inc. -- ANGLE (Intel(R) HD Graphics 5500 Direct3D11 vs_5_0 ps_5_0) -- OpenGL ES 2.0 (ANGLE 2.1.0.316930d51ea9)
     GPU Accelerated Windows: 0

     AzureCanvasBackend: skia
     AzureSkiaAccelerated: 0
     AzureFallbackCanvasBackend: cairo
     AzureContentBackend: cairo

 JavaScript

 Incremental GC: 1

 Accessibility

   Activated: 0
   Prevent Accessibility: 0

 Library Versions

     Expected minimum version
     Version in use

     NSPR
     4.12
     4.12

     NSS
     3.21.1 Basic ECC
     3.21.1 Basic ECC

     NSS Util
     3.21.1
     3.21.1

     NSS SSL
     3.21.1 Basic ECC
     3.21.1 Basic ECC

     NSS S/MIME
     3.21.1 Basic ECC
     3.21.1 Basic ECC

As you are getting an SSL error issue, the first thing I would try is altering the pop mail account server settings for 'connection security'. You are using port 110, which is ok, but currently you have 'STARTTLS' and according to the fairpoint info it should be 'none'. As you are getting an SSL error message this is the first thing I would check.

• Right click on pop mail account in Folder pane and select 'settings'
• select 'Server Settings' for the pop mail account
• Connection security: select 'None'
• click on OK

Exit and restart Thunderbird.

You say you spent some time with the fairpoint support, who say your settings are correct, but your settings do not match what they state.

• http://settings.email/myfairpoint.net-email-settings.html

Toad-Hall

thank you for the clear instruction, the last worked, the support person said it had to be 'STARTTLS'