How do I re add my hotmail account to my iMac?

Gary, this is only partially true. Hotmail addresses still work and are maintained. I use more than one hotmail address on several devices/apps, including iPhones etc. It seems that Apple has dropped its level of support. The mail account can still be set up and used. My particular issue is that I can't get the calendar from our shared family hotmail account on my mac, whilst I do still have access on my iPhone and iPad.

Yes, that is exactly my problem.

Setting up an outlook.com or hotmail.com email account via IMAP is possible using the 'Mail account' option in 'Internet Accounts' on an iMac or MacBook. But this WILL NOT allow you to sync your calendar or contacts.

The iPhone allows you to setup 'Mail' -> 'Accounts' with the Outlook.com option, which will also allow you to sync your calendar or contacts. This option is missing from the menu in iMac or MacBook.

This page also describes the problem, if you scroll down all the way:

How do you sync Microsoft Outlook Web Apps's calander to iCal? - Microsoft Community

So the question is to Apple, when they will add the 'Outlook.com' 'Internet Accounts' option to iMac or MacBook.

Hi,

Open the Mac Mail app then go to the Mail menu bar, click Mail > Preferences then select the Accounts tab then selec the Account Information tab then click ➕ under the panel on the left.

Select other mail account then enter your email address and password:

Hotmail addresses are no longer valid, it is now an Outlook address in the form of: jimsmith@outlook.com

Had the same issue. That worked for me.