Gets the list of domains MX lookup succeeded for.
A reference to the StringCollection object which contains the list of all recipients domains, for which MX or A records have been found.
If at least one MX or A record has been reported by the DNS server for the given domain, it means this domain probably has SMTP service running on the host specified by MX/A record, and can accept mail for delivery. Such domain will be placed into SuccessfulDomains list.
SmtpMessageMXLookupDoneEventArgs Class | MailBee.SmtpMail Namespace