problems
With both the old mailman list and this listserv list, we're having a problem of messages not getting delivered. Research indicates that this is caused by yahoo, but as a result it's also affecting gmail and hotmail, and possibly others. There's a long explanation below, including why it's important to do something about it, but the short version is, please contact yahoo if you're using them, and ask them to stop using DMARC to disqualify your messages to mailing lists. Tell them that if the problem persists, you'll switch to another email provider. This might make them change their minds.
Sending a message from a yahoo account triggers it, but then it affects hotmail accounts too, and maybe google. There is nothing we can do at this end (other than drop such accounts from the list) because the mailing list software and server are not at fault.
Yahoo, who runs mailing lists, has broken all other mailing lists. Regardless of intention, this is the fact. [update, it isn't just yahoo now]
We can just succumb and abandon our own mailing lists, go over to yahoo, microsoft or google, (for so long as they don't suspend our accounts and delete everything), or we can object. It's the easiest thing in the world to set up a yahoo, google or facebook group, but it has downsides too. It's no secret that the control freaks desire to control our internet activity, they admit it frequently. What we have to decide is, are we ok with that? Will we just take the easy path, or will we do a bit of work; make a bit of effort in order to leave a useful internet for our children? If we don't control it, someone else will.
Incidentally, none of this has had any effect whatsoever on spam, as any intelligent person could have predicted. But I doubt that was the intention anyway.
Longer explanation.
Yahoo breaks every mailing list in the world
DMARC is what one might call an emerging e-mail security scheme. There's a draft on it at draft-kucherawy-dmarc-base-04, intended for the independent stream. It's emerging pretty fast, since many of the largest mail systems in the world have already implemented it, including Gmail, Hotmail/MSN/Outlook, Comcast, and Yahoo. DMARC lets a domain owner make assertions about the From: address, in particular that mail with their domain on the From: line will have a DKIM signature with the same domain, or a bounce address in the same domain that will pass SPF. They can also offer policy advice about what to do with mail that doesn't have matching DKIM or SPF, ranging from nothing to reject the mail in the SMTP session. The assertions are in the DNS, in a TXT record at _dmarc.<domain>. You can see mine at _dmarc.taugh.com. For a lot of mail, notably bulk mail sent by companies, DMARC works great. For other kinds of mail it works less great, because like every mail security system, it has an implicit model of the way mail is delivered that is similar but not identical to the way mail is actually delivered. Mailing lists are a particular weak spot for DMARC. Lists invarably use their own bounce address in their own domain, so the SPF doesn't match. Lists generally modify messages via subject tags, body footers, attachment stripping, and other useful features that break the DKIM signature. So on even the most legitimate list mail like, say, the IETF's, most of the mail fails the DMARC assertions, not due to the lists doing anything "wrong". The reason this matters is that over the weekend Yahoo published a DMARC record with a policy saying to reject all yahoo.com mail that fails DMARC. I noticed this because I got a blizzard of bounces from my church mailing list, when a subscriber sent a message from her yahoo.com account, and the list got a whole bunch of rejections from gmail, Yahoo, Hotmail, Comcast, and Yahoo itself. This is definitely a DMARC problem, the bounces say so. The problem for mailing lists isn't limited to the Yahoo subscribers. Since Yahoo mail provokes bounces from lots of other mail systems, innocent subscribers at Gmail, Hotmail, etc. not only won't get Yahoo subscribers' messages, but all those bounces are likely to bounce them off the lists. A few years back we had a similar problem due to an overstrict implementation of DKIM ADSP, but in this case, DMARC is doing what Yahoo is telling it to do. Suggestions: * Suspend posting permission of all yahoo.com addresses, to limit damage * Tell Yahoo users to get a new mail account somewhere else, pronto, if they want to continue using mailing lists * If you know people at Yahoo, ask if perhaps this wasn't such a good idea https://www.ietf.org/mail-archive/web/ietf/current/msg87153.html