Confused about calendars

[KeenanCannon]

I'm confused about calendars and I need to get a handle on what's going on. Reason being is one particular client, a fairly high status individual who gets invited to lots of different meetings from organizations outside of his own, which consists of just a couple of people, one being a full time personal assistant. His calendar is really packed.

Frequently he'll receive an invitation to some kind of meeting. Organizers are looking for confirmation of attendance. Some calendar / email platforms make this easy, others do not.

I presume that if your audience is "captive" (i.e. an internal office meeting and everyone uses 365) then it's pretty straightforward. But what happens when a meeting organizer uses 365 (or Google Workspace or other) and invites a mix of internal and external users?

Here's what I've determined in my testing:
365 organizer to Google Workspace email user (works)
Google Workspace organizer to 365 email user (works)

So I guess those two combos have the interoperability baked in. But what about other platform users (i.e. @mac.com aka @icloud.com)?

That's my dilemma. This client uses an @mac.com email address. It's his only one and he's really attached to it. Everyone knows him by that address, etc.

I haven't found a way for him to accept invitations from 365 or Google Workspace.

Here's where it gets even messier. He has a Google Account that uses his long-held @mac.com address. But you guessed it... he can't log in. And we can't reset the password, apparently because it's so old he never had to put in a phone number or alternate address. I can try accepting invitations from Google with it but it wants us to sign in. Also, I can't trick it by logging in to a different Google account, it has to be that address.

Invitations from 365 seem to offer no way to let an @mac.com user accept invitation.

Any insights? Thanks!

[albieklimaszewsk]

Calendars can be confusing, especially when dealing with different platforms and email systems. While browsing online, I came across some cool September calendar templates that can be easier to read.