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From: Lyndon Nerenberg <lyndon@orthanc.ca>
To: 9front@9front.org
Subject: Re: [9front] rewrite rules -- explanations?
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Date: Sun, 04 Oct 2020 16:55:00 -0700
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X-Glyph: ➈
X-Bullshit: anonymous decentralized information persistence method 

> The following two don't make much sense to me: What generates
> chains of '@'s, and why do we convert to them before converting
> to '!'? Is this something old email servers used to generate?
> Is it still relevant?
>
> 	# convert source domain address to a chain a@b@c@d...
> 	@([^@!,]*):([^!@]*)@([^!]*)		alias	\2@\3@\1
> 	@([^@!]*),@([^!@,]*):([^!@]*)@([^!]*)	alias	@\1:\3@\4@\2
> 	
> 	# convert a chain a@b@c@d... to ...d!c!b!a
> 	([^@]+)@([^@]+)@(.+)	alias		\2!\1@\3
> 	([^@]+)@([^@]+)		alias		\2!\1

"Source routed" RFC822 addresses have been dead for decades.  Time to
blow that cruft out of the water.