Take the 2-minute tour ×
Server Fault is a question and answer site for professional system and network administrators. It's 100% free, no registration required.

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.

Background:

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 check-auth@verifier.port25.com 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:
http://www.goldfisch.at/knowwiki/howtos/dkim-filter
http://old.openspf.org/wizard.html

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.

share|improve this question

3 Answers 3

I don't think it poses any security "issues", but it seems to be something unique to Yahoo. It seems to be a long way around of putting a unique "serial number" on a message. You'd have to ask them for more information.

share|improve this answer

In general X-headers can refer to any non-standard header added during the sending of an email. X-headers can be added at any stage. Some examples of X-headers are:

X-Mailer:

X-Spam-Reason:

X-DomainKeys:

One of the names Yahoo uses for its own mail system is "YMail", so YMailISG is probably going to be something they add to email passing through their system, most like a message ID of some kind. Beyond that, if Yahoo don't document it anywhere public, anything else from here on in is just going to be guesswork.

share|improve this answer

X-YMailISG is added by Yahoo to all incoming messages. On the flip side, X-YMailOSG is added by Yahoo to all outgoing messages.

I believe (but am not 100% sure) that ISG and OSG stand for Inbound Spam Guard and Outbound Spam Guard, respectively.

share|improve this answer

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.