Example user input: "mail@domain1.com, mail@domain2.com" If you don't check the user input and blindly send an email verification link, this could lead to two

Example user input: "mail@domain1.com, mail@domain2.com" If you don't check the user input and blindly send an email verification link, this could lead to two emails sent out. Depending on the email library you could possibly even add some email headers and misuse your email server to send spam.