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Yes, privacy. If the mail server is internet (or "cloud") based, hiding the IP address by not adding the X-Originating-IP header can prevent information leakage of the sender's public IP address. If the mail server is LAN based, then the server with the last hop before WAN should also remove any Received headers containing private IPs to prevent the ...


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Hiding the originating IP can also help protect against attackers / phishing attackers that gain knowledge of the internal network of companies by getting the ip's of employees from the 'auto' mail replies. But I believe the main reasoning is privacy.


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Is this in any way a threat? No. Your server correctly rejects the mails before they reach your server (the spammer only greeted), so only minimal resources are used and you can just ignore it. How can I stop this person? By blocking such attempts if they do it too often, e.g. using fail2ban, which you can install via package management. It is used ...


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Regarding security, usually such connection attempts are just made by automated spam bots operating from malware contaminated PC. In all case it seems that these requests are correctly rejected by your server. I recommend you to check SPAM protection measures to protect your mail server, and in particular I recommend you to setup a check toward SpamHaus ...


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These records show that this sender is trying to relay mail through your mail server. But fortunately, your mail server is not setup to allow open relaying, so that's preventing these attempts from succeeding. If this mail server is only being used to send outgoing mail, and is not being used to receive incoming mail, then you may want to setup your ...


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It's probably a machine trying to use your mailserver to send spam. To answer your questions: The risk for you here is that, if he succeeds, your mailserver is going to be blacklisted as an Open Relay. You must configure your mailserver to accept connections on port 25 only from the hosts you want to be able to send mail. As an additional protection, ...


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I think the point you're missing is this: SMTP header isn't an attack on a mail server. It is an attack on a web server, or other application that controls a mail server at the back end. See the OWASP page on Testing for IMAP/SMTP Injection. In your question, your definition of a "secure SMTP server" is one that does not support pipelining. Pipelining is ...


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The process of sending the email encompasses the generation of the mail envelope and the mail body. Anything that is not part of the DATA chunk is the mail envelope. This is classic separation of control messages and the data payload itself. And also in similar fashion to other standards, the resultant mail as delivered by the local delivery agent is in all ...


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The SMTP protocol is based on a series of commands and replies. RFC 821 (April 1982) expected that the client read each reply before proceeding. This way, if I send an email to Alice, Bob and Carol, there are many roundtips, as I mut do: "RCPT Alice" (wait for reply), "RCPT Bob" (wait for reply), "RCPT Carol" (wait for reply), . Later, RFC 1854 (October ...



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