Seeing if the server is listening on port 25 and is responding in a manner consistent with a SMTP server and not giving a 521 status code is a pretty safe bet though.

So am I right that, although not 100% reliable, this might be a good way to check if a domain has an actual email with no risk to be caught as spammer? Is there a code which implements this approach?

In reply to Re^6: Determine if domain is actually used for email by vit
in thread Determine if domain is actually used for email by vit

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