In order for us to better investigate this issue you need to add a little more non-personal information.

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.

Please also add the result of these troubleshooting steps to your post

• Does Thunderbird work in TB Safe mode (see Thunderbird Safe Mode)?
• Do you use anti-virus and firewall software? What is the version?
• Who is the email provider?
• Who is the internet provider?
• What is the exact error message?
• What steps did you take right before this happened?

Please post back with this information and any other questions you might have.

Application Basics

   Name: Thunderbird
   Version: 45.4.0
   User Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0
   Profile Folder: Show Folder

             (Local drive)
   Application Build ID: 20160928132736
   Enabled Plugins: about:plugins
   Build Configuration: about:buildconfig
   Memory Use: about:memory

 Crash Reports

 Extensions
   Lightning, 4.7.4, true, {e2fda1a4-762b-4020-b5ad-a41df1933103}
   ESET Endpoint Security Extension, 5.0.2254.0, false, eplgTb@eset.com

 Important Modified Preferences

   Name: Value

     browser.cache.disk.capacity: 1048576
     browser.cache.disk.filesystem_reported: 1
     browser.cache.disk.smart_size_cached_value: 942080
     browser.cache.disk.smart_size.first_run: false
     dom.apps.reset-permissions: true
     extensions.lastAppVersion: 45.4.0
     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.crash-guard.glcontext.appVersion: 45.4.0
     gfx.crash-guard.glcontext.deviceID: 0x0a16
     gfx.crash-guard.glcontext.driverVersion: 10.18.10.3431
     gfx.crash-guard.glcontext.gfx.driver-init.direct3d11-angle: true
     gfx.crash-guard.glcontext.gfx.driver-init.webgl-angle: true
     gfx.crash-guard.glcontext.gfx.driver-init.webgl-angle-force-d3d11: false
     gfx.crash-guard.glcontext.gfx.driver-init.webgl-angle-force-warp: false
     gfx.crash-guard.glcontext.gfx.driver-init.webgl-angle-try-d3d11: true
     gfx.crash-guard.status.glcontext: 2
     mail.openMessageBehavior.version: 1
     mail.winsearch.firstRunDone: true
     mailnews.database.global.datastore.id: 0b15a885-5c7a-45c2-af4a-fb9dc700c58
     network.cookie.prefsMigrated: true
     network.http.keep-alive.timeout: 5000
     network.predictor.cleaned-up: true
     places.database.lastMaintenance: 1477549444
     places.history.expiration.transient_current_max_pages: 104858
     plugin.importedState: true

 Graphics

     Adapter Description: Intel(R) HD Graphics Family
     Vendor ID: 0x8086
     Device ID: 0x0a16
     Adapter RAM: Unknown
     Adapter Drivers: igdumdim64 igd10iumd64 igd10iumd64 igdumdim32 igd10iumd32 igd10iumd32
     Driver Version: 10.18.10.3431
     Driver Date: 2-20-2014
     Direct2D Enabled: false
     DirectWrite Enabled: false (6.3.9600.18468)
     ClearType Parameters: ClearType parameters not found
     WebGL Renderer: Google Inc. -- ANGLE (Intel(R) HD Graphics Family 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

   Does Thunderbird work in TB Safe mode (see Thunderbird Safe Mode)?

Yes but nothing changes, same issue as before

   Do you use anti-virus and firewall software? What is the version?

Yes, Eset endpoint antyvirus v5 and v6, tried turning it off but nothing changed

   Who is the email provider?

home.pl

   Who is the internet provider?

Highnet

   What is the exact error message?

There's no error message, emails just won't download or open

   What steps did you take right before this happened? 

Just what i mentioned above, server timeout from 115 to 10000, removing whole account and downloading it again, archivized mails from older years.

Emails just download in random fashion, sometimes it's all emails from few old days and sometimes it won't download for 2-3 days. After removing all mails from account and downloading it again it downloads to certain point and won't go further for few days.

Also when we access mails from www it's all fine, other account that's on same thunderbird is also fine.

One more thing, when i try to go File->Offline and thunderbird ask me do i want to download all mails before doing this and i click yes then poof magicly all emails are downloaded properly :)