https://doc.sitecore.com/xp/en/developers/exm/104/email-experience-manager/the-emailregexvalidator-and-the-urlregexvalidator-settings.html
The emailRegexValidator and the urlRegexValidator settings | Sitecore Documentation
Overview of the EXM settings used to verify that a string is in a valid email format. To validate a contact's email address and any URLs that a contact clicks...
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