^{Thunderbird has started experimenting with some artificial intelligence features lately. This includes detecting email messages from mother-in-laws and sending them to Trash, but unfortunately it’s not entirely bug-free yet so one of the things that could happen is that it works the other way around, unless that’s the "I can do this too" feature already enabled in addition to the previous one.}

^{No, that’s a joke of course, or at least an attempt to make one - I couldn’t resist mentioning it, sorry. ;-)} If your account is set up as IMAP, first make sure any messages of your son and daughter-in-law show up in the proper folder (Inbox) on webmail before opening Thunderbird to rule out this is a Thunderbird issue. Theoretically and when enabled, a spam filter at the email provider can detect them as such and move the messages to the Deleted/Trash folder.

Also, make sure you have no other email client or device that could be responsible for deleting these messages.

If the above is OK, do you use the Junk mail filtering in Thunderbird? If so, could that be set up to delete messages deteted as junk rather than moving them to the Junk folder (default), and they were erroneously detected as junk? Check Tools (in toolbar menu or using menu button) > Options > Security panel > Junk tab - Move them to the account’s "Junk" folder. In the same dialog and if enabled, you can click the Show Log button to view the junk log and see if that moved the messages.

Additionally, check Tools > Account Settings > Junk Settings for the affected account and make sure everything is set up as you wish. You can disable junk mail filtering entirely, include/exclude both address books, or disable any external software possibly causing their messages to be marked as junk (based on additional headers inserted in the message).

You can also set up some manual message filters (Tools menu > Message Filters), but I don’t think you have any based on their email addresses. Nevertheless, it may be good to check that filter log by clicking the Filter Log button in its dialog - perhaps another filter moved them.

If the above does not help: I have little experience with antivirus or other Internet security software or their features that are capable of "interfering" with incoming email (such as Avast’s Mail Shield feature), but theoretically such software may be able to. Try disabling any external junk features in security software, disable it as a test, or check its features and logs. of course and considering those features, it would be possible both your son and daughhter-in-law’s emails actually contain suspicious or virus content (or they are "false positives"), so that the messages were removed from your Inbox for a valid reason. You could exclude antivirus scanning in Thunderbird in the Security panel > Antivirus tab - Allow antivirus clients to quarantine individual incoming messages.

Please report back if anything helped.

Hi and thanks for your reply, the 'joke'did bring a smile to my face... lol

1. I checked webmail and my son's email was in the inbox there so that is not the problem 2. We have no other email client 3. The 'show log' button was greyed out , so I couldn't look at the log. I have enabled this so if it happens again with their next emails , I can look at the log. 4. I can see nothing amiss in the junk settings, I have 'do not mark as junk if sender is in personal address book' ticked 5. I have checked to see if they have inadvertently been added to our blocked sender filter, but they have not. Again the log button was greyed out so I have enabled that for anything in the future. 6. I can't see anything in Avast's Mail Shield that would cause this problem.

So, all in all, I am still at a loss. I do appreciate your help and many thanks for that, if you can think of anything else I would be very interested. I think all I can do for now is wait for their next email(s) and look at the logs I have now enabled to see if that shows anything

As a test: Lets try to move those emails before Junk Controls does anything. Create a folder called 'Family'.

Create a Message Filter - 'Menu icon' > 'Message Filters' > 'Message Filters' click on 'New' Filter Name: 'Family' Apply filter when: select: 'Getting new mail' and 'Filter before Junk classification' select: 'Match ANY of the following' 'From' and 'contains' and type your son's email address click on the small + sign 'From' and 'contains' and type your daughter in laws email address

Perform these actions: 'Move message to' and select a suitable folder -eg: 'Family' on mail account. click on 'OK'

Make sure that the 'Family' filter is at the top of the list and checkbox is selected so it is enabled. close window - top right X

Now send email to son / daughter in law and ask them to send an email so you can test filter. Wait for new incoming mail. Do those specific emails get directed into the 'Family' folder?

Thank you Toad-Hall, I set up the filter as you suggested and it worked!!

Very grateful for your help

That would leave the junk mail filtering as possible cause. Now try to disable this manually created filter and see what the Junk log says at the next message.

In addition my previous message, Trust junk mail headers set by: in the Account Settings > Junk Settings can of course be disabled too, and the settings in the bottom section should be set not to move such messages to the Other > Trash folder, nor to be automatically deleted after x days.

Thanks Tonnes The Trust junk mail headers set by: in the Account Settings > Junk Settings is disabled and the settings in the bottom section are set not to move such messages to the Other > Trash folder, nor to be automatically deleted after x days.

OK. Since you had the Personal address book ticked, I assume the Junk filtering itself is still enabled ("Enable adaptive junk mail controls for this account"), so you could simply disable that too as suggested.

You can ask your son or daughter-in-law to send two test messages with some time in between while on the phone, and see what happens when junk filtering is disabled first, then the other one when enabled, in which case the log should add an entry if the message goes to Trash. I would be curious to see if this is the case, though the messages should be moved to their appropriate folder and show a flame icon too.

If it turns out not to be caused by junk filtering in Thunderbird; there is a slight resemblance with this question, even though that involves a Mac. As written earlier, do you use any antivirus or other so-called security software software that might be moving the messages to trash? Do both senders’ messages contain signatures with images perhaps? Can you try disabling the Mail Shield section in Avast or uninstall Avast entirely, as well as disable other security software (only when using a router/LAN and you don’t need the firewall component) and reboot?

Remember that most issues like these originate from antivirus products, while in fact you don’t need them for email.

I have had a 'eureka' moment and think I know what has happened!

A couple of years ago we were being bombarded with spam and I set up a 'blocked sender' filter, some of these bogus emails were supposedly coming from email addresses that incorporated our surname and were added to the list. I think that, as our son and daughter-in-law's email addresses also include the same surname, the block sender filter has trashed them, but, rather than deleting them altogether (as they are 'starred' addresses) it just sends them to trash (to 'keep' them). The 'new' filter that has been set up as per Toad-Halls' reply has, in a way, created exceptions to this by filtering out their emails first and thus not trashing them. I hope this makes sense, it does to me anyway lol.

Thanks for all your help guys, it was very much appreciated.

MoniMaiden said

You can also set up some manual message filters (Tools menu > Message Filters), but I don’t think you have any based on their email addresses. Nevertheless, it may be good to check that filter log by clicking the Filter Log button in its dialog - perhaps another filter moved them.

5. I have checked to see if they have inadvertently been added to our blocked sender filter, but they have not. Again the log button was greyed out so I have enabled that for anything in the future.

The solution doesn’t sound right and was merely intended as a test.

Why not just remove the addresses from the existing "blocked sender" filter as kind of suggested earlier, assuming this is an existing and obviously "too agressive" filter in Thunderbird after all (probably also causing log results, so there is no "I think that" ;-) ), rather than creating an exception? You may run into similar issues of not.

I have been through the entries in the blocked sender filter again and found one that in effect blocked all incoming emails containing our surname, This has now been removed and all is working ok now, Many thanks for your help Tonnes, very much appreciated