this post was submitted on 22 Jun 2024
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A tool on Linux to scan for inboxes on other mailservers? (slrpnk.net)
submitted 4 months ago* (last edited 4 months ago) by boredsquirrel@slrpnk.net to c/linux@programming.dev
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I know this is basically a spam tool.

I think to know that you can query some info from a mailserver to test if an address exists.

I would like to find hidden addresses of some companies, for example I want to test if info@companyname.com exists.

Anyone know how to do that?

Update

I learned quite a bit

  • Mailserver block the requests that are used to get a list of inboxes ("accounts")
  • many servers will block mailservers that are not on an allowlist
  • many servers will block servers, if mails were sent to nonexistent addresses a couple of times
  • the message "recipient not known" will not appear often, as servers may "black hole" a senders mail and cut off the connection without sending the status message back
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[–] schwim@lemm.ee 4 points 4 months ago* (last edited 4 months ago)

That might not work either. If a server marks it as spam, we do something called blackholing the email, meaning we discard the email and close the connection without responding to the sending server. This is done in an effort to provide as little info as possible to a bad actor.

If you don't send an email from a server and address deemed reputable and with a low enough spam score, you'll be shut down by more than 95% of the mail servers out there.