A unique email address is required for every user. This ensures that the session history is always valid and unique for that listener. One way to set up a unique email for a client that doesn't have one is to create an alias email. Each email provider has an option to create aliases.
There are quite a few ways to create multiple email addresses in Gmail.
For instance, if your email address is [email protected], any email that’s addressed to either [email protected] or [email protected] will also be delivered to your main inbox since Gmail ignores dots and anything that’s after the plus symbol in email usernames.