I read somewhere recently that Outlook have changed the default server mode from POP to IMAP. The post said that if you still want to use POP, you have to log into the account via the website and change a setting to 'enable POP' or something like that. I don't use Outlook personally so I can't check that for you, sorry. Alternatively you could try setting up your wife's account with IMAP and see if that works. I think the default option for new accounts in Thunderbird is IMAP, so it should be straightforward: https://support.mozilla.org/en-US/kb/thunderbird-and-hotmail

Yes that was the issue. Thanks for the help.