MailMessage.To.Add() throwing exception : “An invalid character was found in the mail header: ‘,’.”

Question

Got the culprit: It’s the extra comma(,) at the end of last email address

mailMessage.To.Add("[email protected],[email protected],");

Remove the trailing comma and it will work:

mailMessage.To.Add("[email protected],[email protected]");

If this does not work in SharePoint then please add each address separately onto MailMessage object like below;

foreach (var address in StringofEmails.Split(",")) {
    MailMessage.To.Add(new MailAddress(address.Trim(), ""));
}