wwwoolf said

MacBook Pro: I have not received any help with this. Cannot use Thunderbird after using it forever. The service provider says it is a Thunderbird issue. It is not occurring with other mail programs on my IpPHone or Ipad

So is there no help? I have had to stop using Thunderbird after a gazillion years. More and more emails are not downloaded so I have had to switch to the server's mail program which is awful

is this an imap or pop account?

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?

Matt said

is this an imap or pop account? 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?

Matt - finally getting back. This is a pop account. I havent used Thunderbird since this email but havent deleted it either. I miss it.

I am using OS 10.10.5 and I just updated Thunderbird to 38.3.0.

I tried the link to Safe Model and got this address   http://mzl.la/1k5DWjq%20Thunderbird%20Safe%20Mode   but a "Page not found" message.  

No virus or firewall...Should I use Norton?

And the email Internet provider is ACS https://www.alaskacommunications.com/

Troubleshooting Information This page contains technical information that might be useful when you're trying to solve a problem. If you are looking for answers to common questions about Thunderbird, check out our support website. Include account names (possibly identifying information) Application Basics Name Thunderbird Version 38.3.0 User Agent Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 Profile Folder Application Build ID 20150928051427 Enabled Plugins about:plugins Build Configuration about:buildconfig Memory Use about:memory Mail and News Accounts ID Incoming server Outgoing servers Name Connection security Authentication method Name Connection security Authentication method Default? account1 (none) Local Folders None Normal password account2 (pop3) mail.acsalaska.net:110 None Normal password mail.acsalaska.net:465 SSL/TLS Normal password true mail.acsalaska.net:465 SSL/TLS Normal password false account3 (pop3) mail.acsalaska.net:995 SSL/TLS Normal password mail.acsalaska.net:465 SSL/TLS Normal password true Crash Reports Report ID Submitted bp-3619d85d-65a7-47e2-884c-be0e02131106 11/6/13 bp-b67df5f3-c8f7-4ce1-a29d-ca9062130202 2/2/13

All Crash Reports Extensions Name Version Enabled ID Lightning 4.0.3 true {e2fda1a4-762b-4020-b5ad-a41df1933103} Important Modified Preferences Name Value accessibility.typeaheadfind.flashBar 0 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 browser.display.background_color #FFCCFF browser.zoom.full true extensions.lastAppVersion 38.3.0 font.internaluseonly.changed false font.name.sans-serif.x-western Bank Gothic font.name.serif.x-western Arial Narrow gfx.blacklist.direct2d 3 mail.openMessageBehavior.version 1 mail.spotlight.firstRunDone true mailnews.database.global.datastore.id 501158f4-1933-3c46-8beb-a6479e50e00 mailnews.database.global.views.conversation.columns {"threadCol":{"visible":true,"ordinal":"5"},"flaggedCol":{"visible":true,"ordinal":"7"},"attachmentCol":{"visible":false… network.cookie.cookieBehavior 3 network.cookie.lifetimePolicy 2 network.cookie.prefsMigrated true network.predictor.cleaned-up true places.database.lastMaintenance 1444372534 places.history.expiration.transient_current_max_pages 104858 plugin.importedState true plugin.state.adobepdfviewernpapi 0 plugin.state.silverlight 0 print.macosx.pagesetup-2 AAAZuDw/eG1sIHZlcnNpb249IjEuMCIgZW5jb2Rpbmc9IlVURi04Ij8+CjwhRE9DVFlQRSBwbGlzdCBQVUJMSUMgIi0vL0FwcGxlLy9EVEQgUExJU1QgMS4w… print.print_bgcolor true print.print_bgimages true print.print_command print.print_downloadfonts true print.print_evenpages true print.print_footerleft print.print_footerright print.print_headerleft print.print_headerright print.print_in_color true print.print_margin_bottom 0.5 print.print_margin_left 0.5 print.print_margin_right 0.5 print.print_margin_top 0.5 print.print_oddpages true print.print_orientation 0 print.print_pagedelay 500 print.print_paper_data 0 print.print_paper_height 11.00 print.print_paper_size 389072 print.print_paper_size_type 1 print.print_paper_size_unit 0 print.print_paper_width 8.50 print.print_printer print.print_reversed false print.print_scaling 1.00 print.print_shrink_to_fit true print.print_to_file false privacy.donottrackheader.enabled true security.disable_button.openCertManager false Graphics Vendor ID 0x8086 Device ID 0x d26 WebGL Renderer false GPU Accelerated Windows 0 AzureCanvasBackend quartz AzureSkiaAccelerated 0 AzureFallbackCanvasBackend none AzureContentBackend quartz JavaScript Incremental GC 1 Accessibility Activated 0 Prevent Accessibility 0 Library Versions Expected minimum version Version in use NSPR 4.10.8 4.10.8 NSS 3.19.2 Basic ECC 3.19.2 Basic ECC NSS Util 3.19.2 3.19.2 NSS SSL 3.19.2 Basic ECC 3.19.2 Basic ECC NSS S/MIME 3.19.2 Basic ECC 3.19.2 Basic ECC

Ok, pop mail is usually removed from the server upon download, other settings are remove from the server when deleted in Thunderbird/Mail client and leave on server. IMAP acount are synchronised.

What this means in a POP mail settings is. If your other dvice deletes the mail on the server, either through download or deletinon on an MAP enabled device that the mail is no longer available for download. That is what I think is happening in your case.

Another possibility is that some mail is in a junk/SPAM folder on the server. POP by definition only downloads mail in the inbox.