Old posting but still findable and relevant. Link has changed:

Setting up an Office 365 POP email account in Outlook 2010 or 2013:

http://btbusiness.custhelp.com/app/answers/detail/a_id/19539/c/5088/

Setting up an Office 365 POP email account in Outlook 2011-2016 Mac

http://btbusiness.custhelp.com/app/answers/detail/a_id/30981/c/5169/

also:

http://www.he.k-state.edu/support/instructions/pmailo365.html

At the moment this isn't working for me, but hopefully it's a matter of slogging away.

HTH

I am currently having one heck of a time attempting to get Pegasus to work again following my BT Connect account being migrated to their Office 365 platform; can anyone who has got this working please care to share their settings? It has me beaten right now...

Have you seen this BT Business Help and Support webpage that contains instructions for setting up and Office 365 POP email account in Outlook?

http://btbusiness.custhelp.com/app/answers/detail/a_id/18748

You should be able extrapolate the appropriate settings for use in Pegasus Mail.  If this is old news then please give us a bit more information about what you have done and what failures you are seeing.

You might want to enable internet session logging.  That log can be helpful in pinpointing a point of failure during a connection.  Be careful about posting a copy of the log file.  Read the help file for details.

Yes, I've seen those settings and I have tried to extrapolate them without success - I've set up Outlook and Outlook Express with no problems.

 I'm right up against a work deadline (sod's law), I'll muddle through and return shortly with some more info on exactly what I'm seeing - thanks for your help, it's appreciated.