EAC/Lightning Sync: Event Attendees are getting removed after the Sync

Issue:

Attendees are being removed from Business events in the Salesforce calendar shortly after being added. Attendees from a Lightning Sync Event get removed if the attendee has a non-primary (alias) email address in the user detail page

What is a non-primary or alias email address?

When you have more than one email address: firstname.lastname@yourcompany.com, sales@yourcompany.com, or support@yourcompany.com and all of these emails allow you to receive emails at <firstname.lastname@yourcompany.com> without having a separate inbox for each of the emails, the email - <firstname.lastname@yourcompany.com> is the primary email address and others are the non-primary or alias email addresses.

If the Attendee has any of the email aliases as the email address in his/ her user detail page in Salesforce, the attendees will be removed from the event: as the user’s email service gives a different email address [primary email: <firstname.lastname@yourcompany.com>] whereas Salesforce contains the user’s alias in the details, leading to a mismatch of the data.