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Comment on Privacy Concerns of a Misspelling an Email Address?

Lack of an MX record would normally cause the sending mail server to generate an NDR with something along the lines of "bad domain." If the sending server attempted to make an SMTP connected to the A record IP, and then there was no response there, I would expect that sending server to generate a similar NDR.

There are legitimate reasons not to send an NDR for undelivered mail. Invalid address (at a valid domain) would be one; this avoids backscatter and footprinting of valid addresses at a domain with brute force random recipients.

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reflex@kbin.social ⁨1⁩ ⁨year⁩ ago
There appears to be one:
https://mxtoolbox.com/SuperTool.aspx?action=mx%3aptoton.me&run=toolpage

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- Nougat@kbin.social ⁨1⁩ ⁨year⁩ ago
  So one of several things happened when you sent that mail:
  
  There was a receiving mail server behind that MX IP which accepted and delivered the mail, either to a named mailbox, or with a "catchall" mailbox, where "unmatched" mail goes.
  
  There was a receiving mail server which did not deliver the mail, because the address was invalid, but did not generate an NDR.
  
  There was not a receiving mail server behind the MX IP, in which case your sending mail server will retry delivery for some period of time, usually measured in days, and when it ultimately fails, then you'll get an NDR.
  
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