what mail provider? Sounds like Gmail and their labels.

I think it is a gmail based email - it is not my regular gmail account but one with a server maintained by my step son - it is an @ family name account and everyone in the family uses it - but i tend to use it for information I can store in folders like outlook used to do - but then i had the disappearing info problem. If I store the info on local folders I will not be able to access the info from other computers - esp important when traveling.

Thunderbird has a load of special code for Gmail accounts. None of which would be triggered by a personalized domain.

Is there a web mail? Your last response indicates there is. can you check what labels are attached to a mail your intending to delete?

Does the server have an all mail folder?

Thanks Matt - I am not very technical so I am not sure what you mean by your questions - i just did some tests by writing emails to myself - putting them in folders and then deleting sent - if they were on the regular ( not local ) folders it disappeared. There is an all mail but I deleted things from it too not realizing what I was doing.

Usually I forward things from my regular gmail so there is no  "sent" to delete from Thunderbird.

I just noticed a few weeks ago that I was missing info I knew I had stored and then I started to figure it out.    I think it is because it is gmail based  - but has all the folders  which fool me.  believe me - I am a very confused senior!

Usually people keep 'Sent' emails in the 'Sent' folder as it is easy to search, locate etc.

Any emails older than a couple of months can be archived. This would keep the folder smaller in size and you can still see old emails via the Archives folder. If gmail, then the designated archives fodler is 'All Mail' If not gmail see Archive Options:

• https://support.mozilla.org/en-US/kb/archived-messages

As you have been deleteing emails from the Sent folder. There may be many 'marked as deleted' emails hidden from view but using up space. Right click on 'Sent' folder and select 'Compact' to remove all traces of old deleted emails.

If the account is set up like or is gmail: 'All Mail' is like an archive. All emails are stored in 'All Mail'. Labels (which you may know as 'folder' names) are applied to emails so that they can also show up in various folders. Deleting an email from a folder does not necessarilly delete from All Mail', but deleting from 'All Mail' deletes from all folders.

Local Folders is not connected to any imap account, so emails will be stored on your computer.

• http://kb.mozillazine.org/Deleting_messages_in_IMAP_accounts
• https://support.mozilla.org/en-US/kb/thunderbird-and-gmail

It is deleting the mail in the all mail folder that is causing you issues.

Gmail places ALL mail in that folder and creates what we see as folders by placing tags on those mails. Mail tagged as Sent appears in the sent folder if it is also in the inbox it also carried a tag of inbox and so on.

You can not delete mail from the all mail folder and expect it to stay around. Better to simply unsubscribe from it

Right click the folder and select subscribe and deselect "all mail". Then again right click and select settings and in server settings, select the advanced button and make sure only show subscribed folders is selected.

Thank you both Matt and Toad-Hall - I am learning a lot about my Thunderbird email account. My regular email is a basic g-mail - with all the tags and labels and long conversation threads which as a former outlook user ( in my work days) confused me a bit. So I started to use my Thunderbird account ( which i believe is managed by google) because I set up lots of folders and sub- folders so it resembled my old work outlook.

So I will take all your suggestions and keep my sent mail and archive mail etc, to the best of my very limited ability.  so I don't loose the info.  I thought cleaning up the sent box was a great idea - but i learned a lesson,  Thanks again -