Can someone elaborate how syncookies cause grief for mail relays

["Yusuf Goolamabbas" <yusufg@xxxxxxxxx>]

Hi, I seem to read conflicting views on whether turning on
tcp_syncookies is a good or bad thing.

The docs mention this

syncookies seriously violate TCP protocol, do not allow to use TCP
extensions, can result in serious degradation of some services (f.e.
SMTP relaying), visible not by you, but your clients and relays,
contacting you

Can someone elaborate on this ?

Also, Dan Bernstein has a page on syncookies which alludes to some
unanswered questions with some prominent linux developers

http://cr.yp.to/syncookies.html

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