You can use Matches activity and pass your Input string and use the below-mentioned pattern to extract only Mail ID from it,
If there is no separator between the lastname and the email id then, it is not possible to extract the email id alone, we need to know which is the lastname, using that we can split the string and get the email id without any other manipulations.
From where you are getting this string, if you are getting it from the outlook, you can get the email id from their active directory instead.
You can try with matches activitiy in Uipath
Already regex pattern is predefined for email so u can easily extract the email from the input string and get the results
Hope it helps you