Options for temporary operational solution to DMARC problem

[Ted Lemon <[e-mail]>]

My understanding is that there are really four possible approaches:

Bounce messages from sites that have p=REJECT; users at those sites have to use some other email address for IETF business.
Rewrite From: header on messages from sites that have p=REJECT to point at discard address
Rewrite all From: headers to point at discard address
Rewrite all From: headers to reply to addresses that forward to senders for senders with p=REJECT

What it means to rewrite a From: header to point at a discard address is probably that the mailbox name will be changed to some admin address that is silently discarded, and the display name will be changed to add "via mailing-list".   So e.g., Ted Lemon <[e-mail] <mailto:[e-mail]>> would be changed to Ted Lemon via ietf <[e-mail] <mailto:[e-mail]>>.   For extra credit, [e-mail] <mailto:[e-mail]> could drop silently if the To: and Cc: headers contain multiple addresses, but generate a bounce if the _only_ address is [e-mail] <mailto:[e-mail]>.   There would probably need to be a list ID so that the bounce message could make sense—it would probably say something like "you tried to reply to sender, but it didn’t work, here’s why, here’s what to do."

Advantages of 1:
Relatively easy
Does not alter sender information, so no unexpected behavior in MUAs
Supported by mailman.
Disadvantages of 1:
Substantial inconvenience for people who are unfortunate enough to work for orgs that use p=REJECT
Possible snowball effect if more sites adopt p=REJECT (e.g., gmail.com <http://gmail.com/>).
Requires checking p=REJECT when processing mail

Advantages of 2:
Does not inconvenience senders from sites with p=REJECT
Minimizes whose headers are rewritten
Supported by mailman
Disadvantages of 2:
Lots of moving parts (e.g., have to check p=REJECT when processing mail)
Email from senders at sites with p=REJECT can’t be sorted the same way mail from other senders can be; inconvenient for users who use rule-based sorting on IETF lists
Harder to send off-list replies if sender is from site with p=REJECT; reply-to-sender in MUA will be handled as described above.

Advantages of 3:
Does not inconvenience senders from sites with p=REJECT
Does not require checking to see whether p=REJECT is in effect for a particular user
Disadvantages of 3:
Email from all senders can no longer be sorted as before, so everybody’s procmail filters, etc, break maximally
Harder to send off-list replies, reply-to-sender in MUA will be handled as described above.

Advantages of 4:
Doesn’t inconvenience any mailing list user
Behavior is as it always was
Disadvantages of 4:
Requires state for each sender from a site with p=REJECT
Possible resource exhaustion attack
Probably requires substantial programming and testing work; risk of data loss
Would take a long time to deploy; might not be quicker than waiting for ARC outcome

I think it is really up to the IESG to decide which of these plans to adopt.   However, if people are interested in talking about what to do, I think this is a decent enumeration of the options (please correct me if I am wrong).   My personal opinion is that option 2 is the least disruptive option, and I believe it is supported by mailman.   Option 1 is the most technically correct option that we have right now, but I think technical correctness is not the right value to optimize for _right now_.   Technical correctness can be restored once ARC completes and is deployed at the sites we are having trouble with; right now, I think the solution that removes the most pain is the best one.

I mentioned options 3 and 4 for completeness, but I think 3 is unnecessarily heavy, and option 4 is too much work.