Modifying existing users on Amazon Connect.

Yes, it is possible to add a secondary email address to existing users in Amazon Connect. You can do this by editing user information either individually or in bulk.

For individual users, you can update their identity and contact information, including the secondary email address, using the Amazon Connect console or programmatically via the API or CLI. Specifically, you can use the UpdateUserIdentityInfo API or the update-user-identity-info CLI command to modify this information for an individual user.

If you need to add secondary email addresses to multiple users, you can use the bulk edit feature in Amazon Connect. To do this:

1. Log in to the Amazon Connect admin website with an account that has "Users - Edit" permissions.
2. Navigate to the User management page.
3. Select the users you want to update.
4. Choose "Edit" to enter bulk edit mode.
5. On the Bulk edit page, you can update the secondary email addresses for the selected users.

It's important to note that if you provide a secondary email address, the user will receive email notifications (except for password reset notifications) to this email address instead of their primary email address. This applies to Amazon Connect instances that are not configured for SAML and use the "Store users in Amazon Connect" option for identity management.

The secondary email address, if provided, should follow the pattern: (?=^.{0,265}$)[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+.[a-zA-Z]{2,63}

By adding secondary email addresses to your existing users, you can enhance communication flexibility within your Amazon Connect instance.
Sources
Add users to Amazon Connect - Amazon Connect
Edit users in bulk in Amazon Connect - Amazon Connect
UserIdentityInfo - Amazon Connect