Input fields: Best practices for validating emails in a text area

I want to allow my users to add email recipients in a text area by simply writing their addresses manually or by copying and pasting them from somewhere; E-mail addresses are separated by a comma or a new line.

How to validate an email address?

If it is an incorrect address, say, john.doe @ example, com, how do you tell the user that it is incorrect?

If it is an incorrect address, let's say, john.doe @ example, comHow do you tell the user that it is wrong?

A) Show them a notification in the text area?

If you have several errors, you can always expand the notification below and make it scrollable.
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SECOND) Offer a suggestion / notification?

This option would be very frustrating when the user has several errors.
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DO) Do you offer any validation at all?

AFAIK, the email validation is not 100% accurate, regardless of what you do, you can never take into account all the vanguard cases. Therefore, you could end up creating a nuisance if you do not validate a legitimate email.