It means abc@abc.com isn't a valid mailbox on the abc.com domain. Therefor the mail cannot be sent to that address, resulting in an smtp failure. Try replacing abc@abc.com with a valid address, and you'll see it works
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"Good judgement comes from experience, and experience comes from bad judgement." - Fred Brooks
You're connecting to an SMTP server but you're not actually logging in to the SMTP server. Since most SMTP servers require some sort of authentication, that is probably where your problem is at.