Hi Wong.

Thank you for this report.
I did investigate and fixed mailing-list integration.

>What changed?

This is caused by redmine's minor upgrading. I couldn't find this
breaking API changes at this time.

> It's not just my emails, either, [ruby-core:70979] (kosaki)
> for https://bugs.ruby-lang.org/issues/11473 is missing, too.

Sorry for your inconvenience experience.

Thanks.