[Mailman-Users] Which user is harvesting sender emails?

Mark Sapiro mark at msapiro.net
Thu Aug 18 20:12:24 EDT 2016

On 08/18/2016 04:55 PM, Steven D'Aprano wrote:
> On Thu, Aug 18, 2016 at 04:36:58PM -0700, Mark Sapiro wrote:
>> Altering the From: based on recipient can be done by modifying the code.
>> Say you have a message "From: Ann User <ann at example.com>" and you want
>> to change that to "From: Ann User <ann+xxx at example.com>" where xxx is a
>> unique code for each recipient.
> Isn't that risky? Not all mail servers understand +xxx addresses. 
> (What's the official term for that?) I know of at least one domain that 
> uses -xxx instead, because they found too many broken mail servers that 
> claimed that + was not legal in an email address.
> The point is that if you mangle the address in this way, and people 
> email Ann+xxx at example.com, there's a good chance that it won't be 
> delivered.

Yes, it's risky for the reasons you suggest. Putting the code in the
Subject: as Richard asks in a follow up is much safer.

> I'd be more inclined to look at the IP address where the spam is coming 
> from. Does it match one of your users? Then they are likely the culprit 
> (or rather, more likely a bot on their machine is the culprit).

Good point.

Mark Sapiro <mark at msapiro.net>        The highway is for gamblers,
San Francisco Bay Area, California    better use your sense - B. Dylan

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