The list of factors that are applied in safe mode are here:

http://kb.mozillazine.org/Safe_Mode

The most likely ones are incompatible add-ons, which you apparently have tested, broken layout (fixed by 'reset toolbars & controls', 'make changes & restart' in safe mode prompt), and hardware acceleration (disable it in Settings/General in normal mode, restart TB). Try those fixes and see if downloading works in normal mode.

Hi

Thanks for the reply. I have managed to investigate further and it seems that for some reason the POP3 settings I have used for years no longer work. Originally I used Port995 with SSL/TLS and Normal Password. I changed it to Port 110 with STARTTLS and Normal Password and I can now download my emails. Not really happy though as Port 110 is unencrypted so it seems that something has changed in the encryption system but no idea what. I also found with a second account that the POP3 settings no longer worked. Originally Port 995 with SSL/TLS and Normal Password but had to change to Port 110 with NO security. This seems to confirm that some problem has arisen with the security encryption system. I am particularly unhappy with this situation

I also used port 587 STARTTLS for SMTP but again it failed to send until I changed the port to 465 with SSL/TLS.

This is a problem for me as I travel in Europe on occasions and most of the hotels block port 465 for some reason and I need to use port 587.

Hi again

Just checked email on my phone and it downloads fine using 995 and SSL so the problem does not lie with the servers.

Who is the mail provider? In most cases, POP on 110 is with no security, but IMAP on 143 with STARTTLS is fairly common.

If you are in locations that don't allow port 465, it's possible to set up e.g. a gmail account and use its smtp to send from non-gmail accounts, on 465 or 587.

Also, state your antivirus and VPN if in use, as these can interfere with secure connections even when the server settings are correct.

Hi

Thanks for the advice.

The problem is identical on two different ISPs, TSO Hosts and Zen.

I do not wish to use IMAP as I am sometimes in an area where mobile dongle reception is very poor and I prefer to have the emails available on my laptops. In any case the problem has just arrisen on settings which have worked fine for m any years and only seems to have started when Windows 11 did an update a week or so ago and I updated to version 115. However I have uninstalled the Windows update and reverted to version 102 with the problem remaining. I have also disabled my Antivirus (Eset) and Malwarebytes without any change. It is a problem on my machines as the original settings work fine in Safe Mode which eliminates a problem at the ISP end. I have tried both with and without VPN (NordVPN) connected and it still stays the same. It was still a problem when connecting to my ISP by landline and using a mobile data dongle. Strange but it still works fine on the original settings on my phone and Kindle which again points to a problem on my laptop/desktop setup. Just for fullness I experience the same problem with my email accounts in Gmail, Outlook and Live but as they are all set to auto forward to my main Email address it is not really a problem and they do not really get much traffic anyway.

Just to add to the confusion,

I also have Mailwasher installed on my computers using POP3 995/SSL/TLS which were the settings I originally used in Thunderbird before the problem arose. So on my laptop and desktop using Mailwasher they work fine but I have the problem in Thunderbird unless I change the port/Security protocol as stated above. This is now really bugging me and I am more than ever convinced of a conflict between Win 11 and Thunderbird security protocols.

I am having the same issues, but I am using Win 10. I can send random emails, but ones I really need to send won't go.

Sorry to hear that. My problem is with receiving (POP3) but yours with sending (SMTP), Try changing the SMTP port settings to

465 with TLS/STARTTLS or Port 25 (or 26) with no security settings ie no SSL or TLS.

See if that helps. If it does.

Make a note of the settings you currently have before changing them.

I think it would be a good idea to do some tests with Windows running in safe mode, to bypass startup apps like ESET, MWB, Mailwasher, VPN, all of which could be interfering with TB performance. This is a more effective method than simply disabling apps, which is not always successful.

Hi

As the title to this thread says, it works fine in Safe Mode in the original set up. That is the main reason I am convinced it is a conflict with Windows 11 and Thunderbird 115.

It also made no difference when I disabled all the startup programs. It was still not connecting.

I understood that your original post indicated it worked in TB safe mode, not Windows safe mode. If you really meant Windows safe mode, then it points to one of your startup apps as causing the issue, as mentioned in my previous reply.

Sorry I was unaware that Thunderbird itself had a Safe Mode. I will look into that later. I anticipated your advice that it could be a Start Up App but I also said I disabled all of them, rebooted and it made no difference.

Hi again

OK checked it out and it is now called Troubleshoot Mode. I did try that initially and did disable add-ons and it made no difference.

Hi Thanks for the advice. The problem is identical on two different ISPs, TSO Hosts and Zen.

Confirm that you are using the settings recommended by these services:

https://help.tsohost.com/knowledge-base/article/12587 POP or IMAP

https://www.zen.co.uk/help-support/emailsetup POP only

Hi

Thanks for the links. The one for TSO only deals with IMAP and I need POP3. The Zen link is good but I was already configured in compliance.

Just to sum up the settings I have used for TSO and Zen for several years, without any problem on several computers on my network, were:

TSO POP3 995 SSL/TLS SMTP 465 SSL/TLS or when abroad 587 STARTTLS Both with Normal Password.

ZEN POP3 995 SSL/TLS SMTP 587 STARTTLS Both with Normal Password.

These settings currently work fine in Mailwasher

These worked fine in Thunderbird until Tuesday morning 29th Aug as did my email accounts set up for POP3 for Gmail, Live and Outlook. These also ceased to work at the same time but were not critical as they are all set to forward to my main TSO email account.

Currently in order to use my email I have had to change only the POP3 settings (SMTP still worked fine) to

TSO 110 None ( It would not work with SSL/TLS or STARTTLS)

Zen 110 None ( It would not work with SSL/TLS or STARTTLS)

To add to the confusion my wife's laptop settings were exactly the same as my original settings and It has continued operating as normal.

This is the situation when I connect through my landline ISP (Zen) both using No VPN and using my NordVPN active AND if I connect via my mobile data dongle connection.

The original settings work fine in Windows Safe Mode but not in Normal.

I have tried Thunderbird in Troubleshoot Mode with all add-ons disabled.

I have tried Thunderbird in Normal Mode with Windows start-up add-ons disabled.

I am still of the mind that this is a conflict between Thunderbird latest version 115.2 (and previous 115 versions) and Win 11 latest version 22H2 22621.2215 although I did uninstall it and the problem remained the same. I also uninstalled Thunderbird version 115 and then installed Thunderbird 102.15.0 and still had the problem. My main suspicion is that the culprit is the Win 11 update I installed sometime early last week so I wonder if anyone else has experienced this problem.

I remain puzzled and can't really think of anything else to check without a complete reinstall from scratch which at the moment I am not willing to contemplate particularly on this current laptop (I am at my holiday caravan for the next couple of weeks) as it had a reinstall from scratch only about a month ago.

OK

I tried another approach.

I had a computer with Win11 22H2 fully updated but never had Thunderbird installed.

I first installed version 102 and it worked fine with security settings. I then uninstalled it and then installed V115.2.0 with a new profile and it worked in SSL?TLS.

I then connected it to the profile on my laptop and it worked fine with SSL/TLS.

Then I went back to the laptop and uninstalled Thunderbird using IOBit Uninstall which also cleared all t6he registry entries.

, Rebooted and reinstalled V115. Connected to the profile that worked with security enabled and it refused to connect until I reset to port 110 with no security.

Now I am really baffled and thinking of waiting till I get home again and doing a clean Windows install and seeing what happens. Not looking forwward to that as it will be on several machines.

I think your test indicates the W11 computer has a different set of external apps, such as antivirus etc., that aren't interfering with TB. Instead of doing a clean install of Windows on the laptop, I would first remove (not disable) ESET, MWB, Mailwasher, VPN and any other extraneous apps that run in the background, and see if TB works with the laptop profile.

Hi Thanks again for your input which I greatly appreciate.

I am somewhat restricted as to what I can do on the laptop which, while I am here at my holiday caravan, is my main access to the internet so I do not wish to fiddle too much and end up with other problems. The second computer is a desktop which is used mainly for playing video files downloaded from the web. Having said that the installation of Windows and programs follows a similar, often identical pattern so the desktop also has all the programs you mention, except Mailwasher, installed. As Mailwasher is installed on the laptop and works fine with encrypted modes I can't see how that could cause a problem. However I will install it on the desktop just to be sure that is not causing the conflict. Apart from that the installation of other software is almost identical on both machines as I have a written procedure which I follow on every new installation/reinstallation. The installation on the laptop of Win 11 is in fact only about a month old.

What I would like to know is where the encryption software is installed. Is it part of Windows or Thunderbird. Because all computers were working fine in encrypted mode until last week when I installed the latest Windows update and the new version 115 of Thunderbird I am guessing that this is when the problem started and the incompatibility arose. Having thought about this I think I will wait until I get home and the second Tuesday of the month is issued by MS together with any Thunderbird updates which are issued up to that date. Any bugs just might be sorted by then. Although it is a possible danger not using encryption I can bear with it for a short time but not long term.

I have also asked both my ISP helplines (TSO and Zen) if they have any ideas so I am in stasis for a short while before making any final decision.