In Tools/Account Settings, in the Copies & Folders section for the account, do you have 'Place a copy in' checked? It should be unchecked, as Hotmail/outlook.com accounts automatically copy sent messages to the Sent folder. Do all sent messages fail to appear in Sent, or just ones that e.g. have attachments? If you send a message from the Hotmail website, is it copied to Sent?

Thank you for your very quick reply. My "Place a copy" was not checked. The messages that failed to appear did not have attachments. I sent a message from the Hotmail website to my second e-mail address (PlusNet) and the copy did appear in the Website sent folder. It also appeared in the sent folder in Thunderbird. Several test messages I have sent from Thunderbird have all appeared in the Thunderbird sent folder, so the problem seems to have gone away. The action I must try if it occurs again is to send a message from Hotmail in my browser! Best wishes.

Lampman said

The messages that failed to appear did not have attachments. Several test messages I have sent from Thunderbird have all appeared in the Thunderbird sent folder, so the problem seems to have gone away. The action I must try if it occurs again is to send a message from Hotmail in my browser! Best wishes.

So, did the messages that failed to appear reappear, or are they still not there?

The missing messages have not reappeared in either Thunderbird of Hotmail

Maybe they never got delivered (didn't leave the Outbox), or are still saved in Drafts. If you search for them in Tbird or Outlook website, are they found anywhere? Did you ever get a reply to them?

They are not in Drafts or Outbox. Nothing showed in the Sent folder after 18 Mar till 22 then nothing till I sent from Hotmail on my browser on 29th. There would have been several messages sent in the gaps, not all would have called for a reply or action, but I am not aware of any not reaching the recipient.

The problem has been mentioned on Microsoft pages, spread over several years, but I was not able to find a useful solution.

Did any of those that needed a reply/action receive one? I have used Hotmail/Live/Outlook.com for over a decade and have yet to see anything like this. Were these automated replies or did you manually compose and send them? Any indications at all that the messages were indeed received and acted upon by the recipients, for those that needed such action?

As far as I am aware, all. All manually composed. In the past I have looked for a message, sent some time previously, and not found it, so suspect some have been missed in the past. But the sent box has quite a large number there over a long period. I have just noticed that the box with the green bar that appears when a message is sent also says "Copy sent to Sent Folder" I haven't noticed this before but suspect it's been there. I will keep a close eye on it in future.

Keep us posted. Microsoft Support may also be of help with recovery of said emails, assuming they actually made it to the online Sent Folder in the first place.

I have just resolved a similar problem setting up a PlusNet account. When I tried to send a message from TB, the message was sent out and then a popup box appeared saying "Copying to Sent folder" (or something equivalent). This copy never completed and I would have to force the box to close. The message was received by the recipient but no copy was placed in the Sent folder. SOLUTION: In the account settings for "Copies & Folder" under "Place a copy in", uncheck the default "Sent folder on " and check the "Other" option, then select the Sent folder from the drop down along side. I suspect this problem is because the PlusNet setup places the Sent folder as a subfolder of the Inbox not alongside it. I am assuming the default option is not expecting this.

SandnetDad said

SOLUTION: In the account settings for "Copies & Folder" under "Place a copy in", uncheck the default "Sent folder on " and check the "Other" option, then select the Sent folder from the drop down along side. I suspect this problem is because the PlusNet setup places the Sent folder as a subfolder of the Inbox not alongside it. I am assuming the default option is not expecting this.

That's right. There are countless mail service providers in existence and each of them has their own policies in place, and how their mail service is implemented and managed will differ from other providers. Thunderbird couldn't possibly account for all these providers, so it's the users prerogative to go through the settings of the client they are using to make sure things are configured to suit their requirements. Unfortunately, most of us only find out something is not working as expected after something has gone wrong.

For example, when I added my Outlook.com account to Tbird, I did not know that Outlook.com automatically places a copy of sent items in the Sent folder. Tbird had the "Place a copy" setting enabled by default, so when I sent a test message, I ended up with a duplicate copy of the test message in the Sent folder, so I had to disable that setting. On the other hand, my Gmail account needs that setting enabled, or else nothing will be copied to the Sent folder.

Hi, I have a similar problem in as much when I send an email I get a message displayed telling me message is being saved to my sent folder with the progress bar moving back and forth and this goes on forever with no end result.

  I have checked out if the appropriate check box is ticked  in account settings, copies and folders and all are selected.
    When I then check my sent folder there is no copy of sent email. I use two accounts and it is the same for both. I am

using Linux Mint. Some help and advice please.