Using classic Outlook for Windows in business environments
I have the same thing happening to me, but also with my iPhone and my financial accounts using my email fail getting logged in stating "Server redirect - invalid email address" contact your email provider. I was able to get my email back on my iPhone (after Apple Support removed it trying to fix the issue) but no mail comes through or can be sent from it. Spectrum said it was an iPhone issue.
FYI... They (Spectrum) just moved all their old roadrunner and TW accounts to a new system about 2 weeks ago. The new system is all AI and the techs no longer have access to it to see what the problem is. Same time my emails quit working on Outlook and iPhone. I have all the correct protocols in place, waiting on Microsoft to call me, their automated system sucks. Went on live chat and requested a call back to they can get into my computer to fix the issue. I had my son in law (IT Tech) try to no avail either. Said it must be something with Microsoft or Spectrum in the background not connecting correctly. Spectrums reply is: "Well you can get your emails on our web so what's the problem... Don't use Outlook or your iPhone then"...
I've had this email for 15+ years now and all my important contacts, financial and legal can no longer be logged in to.
Problem is that my financial accounts are now locked because they use your email as a verification of you logging into your accounts.
I think this is more than just a Microsoft issue. Techs seem to have blinders on... They only look at their products and don't care if it will work with other products people use with their services.