You can get the user-name of the user who executed the workflow from a command, but for email id, the API doesn't provide. It can be taken as an improvement for future.
You can use the below cmdlet to get the name of the workflow executor:
But you can make use of this for your requirement if:
1. You create WFA local users with their email IDs as Usernames.
2. If you use Domain Login for WFA, then you can change the User name attribute in WFA Configuration from sAMAccountName to UserPrincipalName i.e. UPN assuming the UPN and Email IDs are same ( they generally are ). Now you login to WFA as user@Domain.com and since this is also the email id, the above api can get it.
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