In order for us to better investigate this issue, we'll need some more information.

Could you please do the following:

1. Open the menu > Help > Troubleshooting Information, then click Copy text to Clipboard.
2. Go to https://pastebin.com and paste the info from your Troubleshooting Information page, then copy the resulting URL.
3. Open a reply to this post, and paste the link to your troubleshooting information.

Next, we'll need you to provide answers to the following question:

• Does Thunderbird work in 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?

Hi Matt. Thanks for this reply. I copied the troubleshooter info onto pastebin, but couldn't get any further because I didn't know what 'the resulting URL' is. (I'm sorry, I know nothing about computers!)

I'm also struggling to find some of the other info you have requested.  The fault is only intermittent.  I had noted down some of the error messages, but am having to build up a list.

This reply is just an interim one to let you know I appreciate your help and am not ignoring you.

just come to a reply here on the forum and paste your troubleshooting information in. It might complain thee is to much of it, but all the stuff at the end is probably not going to help, so if it complains just paste it into notepad and delete the stuff after the security program and copy that to paste.

No need for an exhaustive list. If you can come up with one or two that will probably be enough to tell a story.

Hi, Matt.

            Name
           

           Thunderbird
         

             Version
           

           17.0.8
         

             User Agent
           

           Mozilla/5.0 (Windows NT 6.1; WOW64; rv:17.0) Gecko/20130801 Thunderbird/17.0.8
         

             Profile Folder
           

             (Local drive)
           
         

             Application Build ID
           

           20130801144703
         

             Enabled Plugins
           

             about:plugins
           
         

             Build Configuration
           

             about:buildconfig
           
         

             Crash Reports
           

             about:crashes
           
         

             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(imap) imap.plus.net:143NoneNormal passwordrelay.plus.net:587NoneNormal passwordtrueaccount2(none) Local FoldersNoneNormal password
     

       Extensions
     

             Name
           
           
             Version
           
           
             Enabled
           
           
             ID
           
         
       
       
       Test Pilot for Thunderbird1.3.9truetbtestpilot@labs.mozilla.comLightning6.2.4false{e2fda1a4-762b-4020-b5ad-a41df1933103}
     

       Important Modified Preferences
     

             Name
           

             Value
           
         
       

       browser.cache.disk.capacity358400browser.cache.disk.filesystem_reported1browser.cache.disk.smart_size.first_runfalsebrowser.cache.disk.smart_size.use_old_maxfalsebrowser.cache.disk.smart_size_cached_value358400dom.apps.reset-permissionstrueextensions.lastAppVersion17.0.8font.name.monospace.elConsolasfont.name.monospace.trConsolasfont.name.monospace.x-balticConsolasfont.name.monospace.x-central-euroConsolasfont.name.monospace.x-cyrillicConsolasfont.name.monospace.x-unicodeConsolasfont.name.monospace.x-westernConsolasfont.name.sans-serif.elCalibrifont.name.sans-serif.trCalibrifont.name.sans-serif.x-balticCalibrifont.name.sans-serif.x-central-euroCalibrifont.name.sans-serif.x-cyrillicCalibrifont.name.sans-serif.x-unicodeCalibrifont.name.sans-serif.x-westernCalibrifont.name.serif.elCambriafont.name.serif.trCambriafont.name.serif.x-balticCambriafont.name.serif.x-central-euroCambriafont.name.serif.x-cyrillicCambriafont.name.serif.x-unicodeCambriafont.name.serif.x-westernCambriafont.size.fixed.el14font.size.fixed.tr14font.size.fixed.x-baltic14font.size.fixed.x-central-euro14font.size.fixed.x-cyrillic14font.size.fixed.x-unicode14font.size.fixed.x-western14font.size.variable.el17font.size.variable.tr17font.size.variable.x-baltic17font.size.variable.x-central-euro17font.size.variable.x-cyrillic17font.size.variable.x-unicode17font.size.variable.x-western17gfx.direct3d.last_used_feature_level_idx1mail.openMessageBehavior.version1mail.winsearch.firstRunDonetruemailnews.database.global.datastore.id6f258828-79d8-4480-bb5e-3295996db9amedia.gmp.storage.version.observed1network.cookie.prefsMigratedtruenetwork.predictor.cleaned-uptrueplaces.database.lastMaintenance1547383677places.history.expiration.transient_current_max_pages104858plugin.importedStatetrueprint.printer_Canon_MG5600_series_Printer.print_bgcolorfalseprint.printer_Canon_MG5600_series_Printer.print_bgimagesfalseprint.printer_Canon_MG5600_series_Printer.print_colorspaceprint.printer_Canon_MG5600_series_Printer.print_commandprint.printer_Canon_MG5600_series_Printer.print_downloadfontsfalseprint.printer_Canon_MG5600_series_Printer.print_duplex0print.printer_Canon_MG5600_series_Printer.print_edge_bottom0print.printer_Canon_MG5600_series_Printer.print_edge_left0print.printer_Canon_MG5600_series_Printer.print_edge_right0print.printer_Canon_MG5600_series_Printer.print_edge_top0print.printer_Canon_MG5600_series_Printer.print_evenpagestrueprint.printer_Canon_MG5600_series_Printer.print_footercenterprint.printer_Canon_MG5600_series_Printer.print_footerleft&PTprint.printer_Canon_MG5600_series_Printer.print_footerright&Dprint.printer_Canon_MG5600_series_Printer.print_headercenterprint.printer_Canon_MG5600_series_Printer.print_headerleft&Tprint.printer_Canon_MG5600_series_Printer.print_headerright&Uprint.printer_Canon_MG5600_series_Printer.print_in_colortrueprint.printer_Canon_MG5600_series_Printer.print_margin_bottom0.5print.printer_Canon_MG5600_series_Printer.print_margin_left0.5print.printer_Canon_MG5600_series_Printer.print_margin_right0.5print.printer_Canon_MG5600_series_Printer.print_margin_top0.5print.printer_Canon_MG5600_series_Printer.print_oddpagestrueprint.printer_Canon_MG5600_series_Printer.print_orientation0print.printer_Canon_MG5600_series_Printer.print_page_delay50print.printer_Canon_MG5600_series_Printer.print_paper_data9print.printer_Canon_MG5600_series_Printer.print_paper_height -1.00print.printer_Canon_MG5600_series_Printer.print_paper_nameprint.printer_Canon_MG5600_series_Printer.print_paper_size_unit1print.printer_Canon_MG5600_series_Printer.print_paper_width -1.00print.printer_Canon_MG5600_series_Printer.print_plex_nameprint.printer_Canon_MG5600_series_Printer.print_resolution600print.printer_Canon_MG5600_series_Printer.print_resolution_nameprint.printer_Canon_MG5600_series_Printer.print_reversedfalseprint.printer_Canon_MG5600_series_Printer.print_scaling  1.00print.printer_Canon_MG5600_series_Printer.print_shrink_to_fittrueprint.printer_Canon_MG5600_series_Printer.print_to_filefalseprint.printer_Canon_MG5600_series_Printer.print_unwriteable_margin_bottom0print.printer_Canon_MG5600_series_Printer.print_unwriteable_margin_left0print.printer_Canon_MG5600_series_Printer.print_unwriteable_margin_right0print.printer_Canon_MG5600_series_Printer.print_unwriteable_margin_top0print.printer_HP_Deskjet_1010_series.print_bgcolorfalseprint.printer_HP_Deskjet_1010_series.print_bgimagesfalseprint.printer_HP_Deskjet_1010_series.print_colorspaceprint.printer_HP_Deskjet_1010_series.print_commandprint.printer_HP_Deskjet_1010_series.print_downloadfontsfalseprint.printer_HP_Deskjet_1010_series.print_duplex0print.printer_HP_Deskjet_1010_series.print_edge_bottom0print.printer_HP_Deskjet_1010_series.print_edge_left0print.printer_HP_Deskjet_1010_series.print_edge_right0print.printer_HP_Deskjet_1010_series.print_edge_top0print.printer_HP_Deskjet_1010_series.print_evenpagestrueprint.printer_HP_Deskjet_1010_series.print_footercenterprint.printer_HP_Deskjet_1010_series.print_footerleft&PTprint.printer_HP_Deskjet_1010_series.print_footerright&Dprint.printer_HP_Deskjet_1010_series.print_headercenterprint.printer_HP_Deskjet_1010_series.print_headerleft&Tprint.printer_HP_Deskjet_1010_series.print_headerright&Uprint.printer_HP_Deskjet_1010_series.print_in_colortrueprint.printer_HP_Deskjet_1010_series.print_margin_bottom0.5print.printer_HP_Deskjet_1010_series.print_margin_left0.5print.printer_HP_Deskjet_1010_series.print_margin_right0.5print.printer_HP_Deskjet_1010_series.print_margin_top0.5print.printer_HP_Deskjet_1010_series.print_oddpagestrueprint.printer_HP_Deskjet_1010_series.print_orientation0print.printer_HP_Deskjet_1010_series.print_page_delay50print.printer_HP_Deskjet_1010_series.print_paper_data9print.printer_HP_Deskjet_1010_series.print_paper_height 11.00print.printer_HP_Deskjet_1010_series.print_paper_nameprint.printer_HP_Deskjet_1010_series.print_paper_size_type0print.printer_HP_Deskjet_1010_series.print_paper_size_unit1print.printer_HP_Deskjet_1010_series.print_paper_width  8.50print.printer_HP_Deskjet_1010_series.print_plex_nameprint.printer_HP_Deskjet_1010_series.print_resolution0print.printer_HP_Deskjet_1010_series.print_resolution_nameprint.printer_HP_Deskjet_1010_series.print_reversedfalseprint.printer_HP_Deskjet_1010_series.print_scaling  1.00print.printer_HP_Deskjet_1010_series.print_shrink_to_fittrueprint.printer_HP_Deskjet_1010_series.print_to_filefalseprint.printer_HP_Deskjet_1010_series.print_unwriteable_margin_bottom0print.printer_HP_Deskjet_1010_series.print_unwriteable_margin_left0print.printer_HP_Deskjet_1010_series.print_unwriteable_margin_right0print.printer_HP_Deskjet_1010_series.print_unwriteable_margin_top0security.sandbox.content.tempDirSuffix{4ab78f76-e7e8-40fc-84b9-a9f4d4bc8623}
     

   Hi, Matt.  Internet and email: Plusnet

It started months ago and has got worse. I uninstalled/reinstalled and hasn't corrected it. AVG Internet security; Anti-track; PC tuneUp; Secure VPN.

Error messages, sent with original query, now mislaid!

That copy above seems to be only a fraction of what I pasted ! It was full of characters! I deleted details of Graphics, because it said I had exceeded the max size (10,000) by 211.

It is only an intermittent fault, so I haven't tried putting it onto Safe Mode.

Sorry that I am not much help. Geoff

lets try updating you to a newer version. That might help. It will certainly close a lot of security holes that have been patched in the years since 17 was released.

So go here and get a new version to install. getthunderbird.com Support for XP and vista has ended, windows 7 is still being supported by Thunderbird, but I do not know for how long. Microsoft ended mainstream support for windows 7 this month.

looking at the settings you supplied, they do appear to match those suggested by your provider, so perhaps that will not be the issue.

sorry to be a pain! the above link won't work - and I've tried typing it in - but each time it says it can't find the server. I've tried several times and it says the same. (It puzzles me that I only downloaded 17.08 on 14th of this month when I reinstalled it.) I have now found a site: thunderbird.net/en-GB/ and have downloaded 'thunderbird setup 60.4.0exe'. Is that what I need? Is it OK to install that? The site also mentioned Beta - but it sounded as if that was very much still being developed and I don't think I am the right person to be a guinea pig!

I have corrected the URL, but what you have downloaded sounds like it is what you would have got to anyway.

The getthunderbird.com site is only a shorthand redirect to your locale . Although your post has made obvious something I should have worked out myself. getthunderbird.com is not shorter now we have out own web site thunderbird.net So I will change my ways.

Hi, Matt. Thanks for your help. I have now installed the download 60.4.0 exe and we'll see if it solves the problem. I haven't ticked the box to say it's solved; I'll give it a couple of weeks and come back and do so, if everything is OK. I'm delighted (and amazed) to have been able to help you. Again, many thanks for your patience and help. I know nothing about these things, as must have been pretty obvious to you. Best wishes Geoff

Hi, Matt. I'm back, sorry! Since installing 60.4.0 about 3 weeks ago, I'm still getting error messages on about half of what I send, to say that the message has been sent but it has been unable to save a copy into my Sent folder. It gives me an option to save it to my local sent folder; this local save works everytime and I CAN LIVE WITH IT. I am getting messages which, without warning, don't arrive with the addressee - which is NOT acceptable! I wonder if this is a different problem, because I am also getting a lot returned undeliverable, yet the address is perfect and if I resend them to that same address, they will be delivered no bother. I suspect this is perhaps not a Mozilla problem. I shall pursue this with Plusnet. So, thanks for all your help. Geoff TP10PhD