I do not want to import all outlook.com items on Outlook 2016 desktop into a new emclient email account. Does it work to first export selected items from Outlook 2016 to a .pst file, and then import that file into a new email account in emclient, rather than having to immediately put all outlook items into a new emclient email, as seems to be the sole setup option with T-bird?
If the messages are already on the server you don’t need to import anything. Just add the outlook.com account to eM Client and it will sync the messages from the server.
Or, if you import an account from MS Outlook app, it will do the same anyway. It won’t import the messages, just the account, and then sync them from the server itself. Only local data (not synced) will be imported.