Same here. I had a brief period of being unable to access emails via my Outlook 'front end' and webmail earlier this evening. Outlook gave the all too common 'Enter your user name and password for the following server' error message and webmail 'Your mailbox is not available at the moment. Please retry again in one hour and make sure you are using the correct password to access your email from all of your devices'. From past experience, that normally means security have locked the mailbox due to unspecified 'suspicious activity'! The 150 team folk won't know what is going on as they don't seem to communicate with security and vice versa! However, this time Outlook started working again, so the mailbox isn't locked.
However, still I'm having no joy using webmail via IE11, Edge, Opus and Firefox. I get 403 Forbidden type messages from all of them, so it's not a browser specific error. If it doesn't clear by the morning, I'll be chasing 150 customer services for a solution. I've got two open formal Complaints raised about email problems at present. I hope this doesn't make it three! I'll let you know if I get a sensible and relevant answer for a change.