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Can email still be exchanged if only one of the SMTP participants has implemented CSV?

April 26, 2017csv email exchanged implemented participants SMTP

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Can email still be exchanged if only one of the SMTP participants has implemented CSV?

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• A: Yes, although the benefit from CSV will be limited. If the sending side implements CSV, it means that the standard field in the EHLO has registered information available. It does not alter the SMTP protocol at all. If the receiving side has implemented CSV, but the sending side has not, then it will subject the incoming mail to its usual stringent tests for spam. The extra cost to the receiving side will be one failed DNS query for the SRV record. Operators of MTAs are free to change nothing; and things will work about as well as they do now — until spammers escalate things so that overly-broad IP blacklists are applied widely and the MTA’s IP address finds its way onto them. If/when they get caught by that kind of problem, they need to ensure that the EHLO string the MTA uses is a legal domain name (which it should be already), and that they can cause a simple SRV record to be placed under that domain. Alas, if they waited that long, there won’t be time to acquire a goo