I think a useful first step would be to post your Troubleshooting Information. That will avoid a lot of question asking and replying.

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.
• Clear the check box Include account names.
• Use the button Copy text to clipboard to select all.
• Paste this into your reply to this forum.

You can trim off the big section at the end about printers and fonts.

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?

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

Application Basics

   Name: Thunderbird
   Version: 52.5.0
   User Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.5.0
   Profile Folder: Open Folder

             (Local drive)
   Application Build ID: 20171121193617
   Enabled Plugins: about:plugins
   Build Configuration: about:buildconfig
   Memory Use: about:memory
   Profiles: about:profiles

 Mail and News Accounts
   account1:
     INCOMING: account1, , (pop3) pop.outlook.com:995, SSL, passwordCleartext
     OUTGOING: , smtp.outlook.com:587, alwaysSTARTTLS, passwordCleartext, true

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

   account3:
     INCOMING: account3, , (pop3) pop.outlook.com:995, SSL, passwordCleartext
     OUTGOING: , smtp.outlook.com:587, alwaysSTARTTLS, passwordCleartext, true

 Crash Reports

 Extensions
   Lightning, 5.4.5, true, {e2fda1a4-762b-4020-b5ad-a41df1933103}

 Important Modified Preferences

   Name: Value

     accessibility.typeaheadfind.flashBar: 0
     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: 52.5.0
     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.d3d11layers.appVersion: 52.5.0
     gfx.crash-guard.d3d11layers.deviceID: 0x6738
     gfx.crash-guard.d3d11layers.driverVersion: 15.201.1151.1008
     gfx.crash-guard.d3d11layers.feature-d2d: false
     gfx.crash-guard.d3d11layers.feature-d3d11: true
     gfx.crash-guard.status.d3d11layers: 2
     layers.acceleration.disabled: false
     mail.openMessageBehavior.version: 1
     mail.winsearch.firstRunDone: true
     mail.winsearch.global_reindex_time: 1451921426
     mailnews.database.global.datastore.id: aa266f57-7d98-4186-b919-43f0c04f2f8
     mailnews.database.global.views.conversation.columns: {"threadCol":{"visible":true,"ordinal":"1"},"flaggedCol":{"visible":true,"ordinal":"3"},"attachmentCol":{"visible":false…
     mailnews.database.global.views.global.columns: {"threadCol":{"visible":true,"ordinal":"1"},"flaggedCol":{"visible":true,"ordinal":"3"},"attachmentCol":{"visible":false…
     media.gmp.storage.version.observed: 1
     network.cookie.prefsMigrated: true
     network.predictor.cleaned-up: true
     places.database.lastMaintenance: 1512489757
     places.history.expiration.transient_current_max_pages: 61837
     plugin.importedState: true
     security.sandbox.content.tempDirSuffix: {2ffc7945-3e63-4e63-b794-69353d1f4297}

 Graphics

     GPU #1
     Description: AMD Radeon HD 6800 Series
     Vendor ID: 0x1002
     Device ID: 0x6738
     RAM: 1024
     Drivers: aticfx64 aticfx64 aticfx64 amdxc64 aticfx32 aticfx32 aticfx32 amdxc32 atiumd64 atidxx64 atidxx64 atiumdag atidxx32 atidxx32 atiumdva atiumd6a atitmm64
     Driver Version: 15.201.1151.1008
     Driver Date: 11-4-2015

     Features
     Direct2D: false
     DirectWrite: true (10.0.15063.674)
     ClearType Parameters: DISPLAY1 [ Gamma: 2.2 Pixel Structure: RGB ClearType Level: 100 Enhanced Contrast: 50 ] DISPLAY2 [ Gamma: 2.2 Pixel Structure: RGB ClearType Level: 100 Enhanced Contrast: 50 ]
     WebGL Renderer: Google Inc. -- ANGLE (AMD Radeon HD 6800 Series Direct3D11 vs_5_0 ps_5_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

Does Thunderbird work in TB Safe mode (see Thunderbird Safe Mode)? - not tested Do you use anti-virus and firewall software? What is the version? - AVG Who is the email provider? BT Who is the internet provider? SKY

this issue is still not resolved - can you assist please?