I hang out on the Source­Forge-hosted inkscape-user mailing list, where I pick up useful tips for the Inkscape SVG editor (vector drawing program).

For months, the list has been plagued with spam; largely because anyone can send to the list. The policy has been not to require new users to sign up for the list before being able to send questions. This is com­mend­ably friendly and user-centric, but the spam has become a real annoyance.

One of the Inkscape developers finally said that, if a dozen or more people said "yes, restrict posting to list members only" and no-one opposed it, he would lock the list down. I attempted to vote yes and got the following rejection letter from Source­Forge:

<inkscape-user@lists.sourceforge.net>:
66.35.250.206 does not like recipient.
Remote host said: 550-Postmaster verification failed while checking <george@reilly.org>
550-Called:   205.158.62.206
550-Sent:     RCPT TO:<postmaster@reilly.org>
550-Response: 550 <postmaster@reilly.org>: User unknown
550-Several RFCs state that you are required to have a postmaster
550-mailbox for each mail domain. This host does not accept mail
550-from domains whose servers reject the postmaster address.
550 Sender verify failed
Giving up on 66.35.250.206.

Such irony! I had received a similar bounce a few days before from the FlexWiki-Users mailing list, which is also hosted by Source­Forge, when I announced Vim Syntax High­light­ing for FlexWiki.

I don’t own the reilly.org domain. It (and thousands of others) are owned by Ne­tI­den­ti­ty. I had an exchange with their postmaster, who said in part:

I did talk to source­forge. They claimed it is an essential part of their spam filtering process to reject domains that dont have a postmaster mailbox.

I’ve tried that (at least on a test basis) myself and with all due respect to them, it is passe’ … doesnt work too well. And it has the added "advantage" of having to connect back to the sending mail domain every time to see if a postmaster for that domain exists. This holds up email and creates additional smtp con­nec­tions - and hence even more load on mailservers, in the case of domains - with postmaster up and running - that are forged into spam.

I did suggest a few more rather efficient (and practical) filters they could use, but well, they didnt respond to those

He has since added a postmaster mailbox for reilly.org, so I can post to Source­Forge lists again.

The Inkscape vote passed, of course. Only sub­scribers can post now. Non-sub­scribers can also use a webform to send questions, so it’s not a big impairment.