Outlook not working -fix/alternative

I tried downloading Thunderbird (Mozilla) desktop email client today ,added NTLworld IMAP email and it worked instantly , so am now thinking that the issue may be the Outlook app, apparently the IMAP side of it is still in development and we all know how Microsoft like breaking things!

(Thunderbird have a mobile app too if needed , think you have to tweak folder settings to get Sent folder to sync with Desktop)