Proton Calendar prevents users from inviting their own Proton addresses or aliases to events, even when those addresses belong to different calendars.

If I try to invite one of my own Proton aliases (e.g., personal@example.com) to an event created in a different calendar that I also own (e.g., a shared team calendar), Proton blocks the invitation. Inviting my own addresses should be allowed when the invited address is not the owner of the originating calendar.

Why this matters?

Users with multiple Proton calendars cannot keep their schedules in sync, reducing the convenience of shared calendars.

For example, I have:
- a shared “Product team” calendar owned by product@example.com
- a personal work calendar owned by personal@example.com

If an event is created in the shared calendar and personal@example.com is invited, it should block that time in my personal calendar.