What exactly is a X-YMailISG header?

Posted by iainH on Server Fault See other posts from Server Fault or by iainH
Published on 2011-03-04T23:45:08Z Indexed on 2011/11/23 9:54 UTC
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Finally ... our emails are being seen by Yahoo! not as junk anymore. Hurray!

However I notice that the Yahoo! receiving MTA adds in a X-YMailISG header. It's very large ... 2**10 bits?

Now that I've invested too large a chunk of my waking life in crafting our email headers I'm curious to know what an X-YMailISG header is. Can anybody tell me? Does it pose any security / authenticity issues? There's very little intelligible from Google results.


After many days tweaking TXT records in our domain's DNS zone file for SPF and DKIM, I have at last succeeded in generating email from our Drupal site that Yahoo! no longer marks as
X-YahooFilteredBulk and the excellent service [email protected] returns results that show the emails passing SPF, DKIM and Sender-ID checks and appearing to SpamAssassin as ham. Yahoo! even adds a Received-SPF: pass header.

Useful links:

Strangely enough the SPF TXT record needed / allowed a blank key / name field in our registrar's DNS management panel whereas the DKIM record needed the {selector}._domainkey as the key /name of the DKIM strings.

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