Mailing List locked up?

Hi, a client of mine is having problems with his DH mailing list: he’s received a lot of mail from subscribers who haven’t received his weekly newsletter for 2 weeks now. I’ve seen other people post here about their mailing lists locking up, so I’m wondering if this is what’s happening.

Nothing about the mailing list has changed: it still shows up as active in the control panel, and the subscription form on the site still works.

Relevant URL:

I sent a note to support, but figured I’d ask here as well. Thanks for any advice you can offer!

Did you include specific addresses in the support message?

Support already asked me for addresses, so I’ll be sending them as soon as I receive them from the client.

The recent changes that we’ve made to the mailing list system may have set it up so that the recipient’s email address doesn’t show up in the ‘To’ or ‘Cc’ headers. I followed up with you in a bit more detail via email.

Since I didn’t see any obvious bounces for any of these addresses, it seems possible that these people have their mail clients set to ignore messages that don’t have their email addresses in the To or Cc headers. I will look into this in more detail, but that would be my initial guess.