[clug] A story about Yahoo mail, X-YMail-OSG and rfc2822

Nemo Thorx clug at nemo.house.cx
Thu Nov 26 18:55:23 MST 2009

Once upon a time rfc2822 said that email lines should be no more than
998 characters.  http://tools.ietf.org/html/rfc2822#section-2.1.1
Including headers. (section 2.2.3)

So, Yahoo mail is now sending X-YMail-OSG headers in excess of this.

Example of headers found in recent lkml...

$ for i in */* ; do echo -n "$i: " ; egrep "^X-YMail-OSG" $i | wc -c ; done | egrep -v ": 0$"
cur/1258417286.30147_9.falcon:2,: 414
cur/1258470362.15712_3.falcon:2,: 394
cur/1258638662.28969_3.falcon:2,: 354
cur/1258895522.14744_3.falcon:2,: 1114

...and this seems to be breaking some mail clients. (not mutt,
thunderbird or gmail though, but I have graver confidence in some more
proprietry clients). This makes baby Jon Postel weep.

Mainly however, it makes email sysadmins gnash their teeth. (that would
be me)

Anyway, this is informative as much as anything, but I do have on

Does anyone know what X-YMail-OSG is even for? It looks like it could be
a hash (signature?) of some kind, and is full of a-zA-Z0-9_.-

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