Some IMAP accounts only allow new folders to be created under the Inbox folder. YouвЂ™d then have to create these folders as sub folders of the Inbox folder instead. In that case your IMAP account doesnвЂ™t accept any new root level folders. The server responded: вЂInvalid mailbox name.вЂ™. When trying to create the folder it could be that you get the following error Д¬annot create the folder. You can do this via the New Folder button on the Folder tab of the Ribbon. If your IMAP account still doesnвЂ™t hold a Sent Items or Deleted Items folder now, you must create them manually.

Select all the folders that you want to have available in Outlook.Д¬reating a Sent Items and Deleted Items folder.A new dialog should open now with a Query button press this button.Select the Inbox folder of your IMAP account.To see all the available folders for your IMAP account

The most common reason for these errors is that you donвЂ™t have a Sent Items and/or Deleted Items folder in your IMAP account or that you are not subscribed to them yet. (click on image to enlarge) Does your IMAP account hold a Sent Items and Deleted Items folder? Improper detection of the default IMAP folders can lead to a cocktail of errors. Luckily you can easily solve them by assigning the correct folders manually or create them when they are missing. Sadly, this mechanism isnвЂ™t fail safe and when the folders cannot be found, youвЂ™ll encounter these errors. In previous versions of Outlook youвЂ™d had to set the Sent Items folder manually or items were kept locally and Deleted items were marked for deletion in the same folder instead of moving them to a separate Deleted Items folder. One of the IMAP improvements in Outlook 2010 is that it will automatically try to assign the correct Sent Items and Deleted Items folders for your account. I've restarted Outlook but I still get all these errors. If the problem persists, restart Outlook.' The messaging interfaces have returned an unknown error. 'The Deleted Items folder is unavailable.' I get a similar error when deleting a message I'm using an IMAP account in Outlook 2010 and each time I try to send a message I get the following error (but the message still gets sent)

Find sent folder in outlook 2016