Hello @JamesA531 ,   If the webinar attendees were aware they may receive emails from you by registering, then it may qualify as implied permission. For more details on implied permissions, I'd recommend checking these two articles: Understanding implied and express permission for CASL and GDPR Implied permission collection methods that result in quality email addresses You may consider turning on Confirm Opt-In for your account (will require enabling advanced contact permissions if not already toggled), so when you add these contacts you can send a COI email to them. This way they receive the invite, and won't count as active, subscribed contacts until they explicitly opt in.   You can export your existing contacts and use your preferred spreadsheet program to try filtering out the attendees that are already contacts. Beyond that, the other option in the account would require importing the contacts into a new list, and using segmentation or list removal to isolate the new contacts among the attendees.    If you'd like additional insight regarding the attendees' permissions, and how best to manage initial communications and adding them to your account, I'd recommend speaking with our Review team.    See also: Review FAQ ... View more