Outlook/Hotmail has always made a copy of the email as it passes through their SMTP server and places it in the send folder. Is this mail not appearing on the server in a browser in the sent folder?

MS 365 browser site displays email in sent folder. Thunderbird no longer displays/captures it in the sent folder since the 3rd party appl installed their new release.

Is Thunderbird configured to use IMAP for that account? That is how the server side sent folder will sync to Thunderbird.

IMAP outlook.office365.com PORT 993 SSL/TLS Oauth2

Same settings as to when it used to work before the 3rd party installed their new release and used their own email code instead of using Thunderbird.

Those emails no longer show up in any of the 4 instances of Thunderbird(thick client) we have set up for that email address (MS Office 365) even though they are in the web based email sent folder for 365. Vendor confirmed the last release modified the method they use to send emails. If we send an email from Thunderbird the sent copy will then appear in the sent folder.

Can Thunderbird Development determine what method NAPA TRACS application is using to send emails and then provide a code modification to capture them in the Sent folder? Can Thunderbird recommend a change to NAPA TRACS to ensure Thunderbird get them in it;s Sent folder??

Alternately, what if I create a rule in MS 365 Connect Browser email which sends a copy of every email it sends to an additional folder(new) called 'SENT2'? Will this SENT2 folder then be kept in sync with Thunderbird SENT2 folder?

Can you confirm you have the following:

In Thunderbird

• Right click on the Imap Sent folder and select 'Properties'
• Select :'When getting new messages for this account, always check this folder'
• click on OK

Was that setting already selected ?

The following was already checked. When getting new messages for this account, always check this folder

Location: imap://service%40hartmannstowing.com@outlook.office365.com/Sent

Ran Repair just for fun. No change

re : goes to sent mail folder in Microsoft 365 web based email sent folder.

What is the exact name of the sent folder on server as seen in webmail account?

Is it 'Sent' or 'Sent Items' or do you see both?

It sounds like you are putting your sent emails into a 'Sent' folder because that is setting in the 'Account Settngs' > 'Copies & Folders' This is then put in 'Sent' on server. However, Outlook server maybe auto putting same emails sent via smtp server into a 'Sent Items' folder.

In Thunderbird Right click on the mail account name foder in Folder Pane and select 'Subscribe' click on 'Refresh' Do you see both 'Sent' and 'Sent Items' in that list ? If you see 'Sent Items' select it and click on 'Subscribe'

Make sure it also has the Properties setting I mentioned in previous comment. Does it display the emails sent via other setup?

I believe I have followed your instructions accurately. Holy cow, Jeeves! You might have resolved it. I now have 887 items(last one dated 3/13/23) in 'sent items' and 428 in 'sent'. All I had before was just the 'sent' folder and that used to work fine until the third party app put in their new release.

We will be doing a controlled test with the third party app, NAPA TRACS, in a few days.