Is there any way to verify that a domain has an MX record DNS entry from a Xojo desktop app for Mac & Windows clients?
I tried these avenues, but couldn’t get it working fully since I could not return the access to the results of a Shell when I did a Telnet command:
forum.xojo.com/37137-validating-an-email-address/0#p303506
www.webdigi.co.uk/blog/2009/how-to-check-if-an-email-address-exists-without-sending-an-email
On Windows, via shell, you could try getting the results of:
nslookup -type=mx gmail.com
It can timeout - be aware.
MBS (as always 
) has a Method for this VerifyEmail
You can get that info using dig on macOS.
This doesn’t check that the email account exists on that server nor that it will receive emails (mailbox full?), only that the email address format is standard, that the domain is responding and the domain has a mail server running on it.
That said, I shall use it!
AFAIK, this can’t be tested without a valid access to the server. 
MBS Plugins have a lot of DNS classes for Mac:
http://www.monkeybreadsoftware.net/topic-dns.shtml
and Windows:
http://www.monkeybreadsoftware.net/class-windowsdnsrecordmbs.shtml
[quote=367565:@David Cox]This doesn’t check that the email account exists on that server nor that it will receive emails (mailbox full?), only that the email address format is standard, that the domain is responding and the domain has a mail server running on it.
That said, I shall use it![/quote]
Well, it can’t do more. Since we got spam, you can’t check any more for validity of an email account.
The server simply takes all emails, than disconnects. And later it processes email and sends bounces.
Thanks, everyone since I own a license to MBS I will try that first seems cross-platform and that’s what I need the most.