This is a bit of mailing list administratativia.†
More specifically, many of you may have recently been unsubscribed to the Code4Lib mailing list, and this is/was apparently a feature of our mailing list software — LISTSERV. Even more specifically, many of us have been using Gmail accounts or have Google hosting our SMTP servers. In either case, Google servers have been more strict about what gets passed on as “not spam”, and our list’s domain has yet to meet the challenge. The “challenge” includes a mixture of Domain Name Server (DNS) configurations, various types of signatures in the email headers, etc. For more detail, see a Google FAQ.  The good people at CLIR/DLF (Wayne Graham, specifically) are on the case, and the whole thing may be resolved in a week or two.
† Apparently “administratativia” is not a real word, but what the heck.
 FAQ - http://bit.ly/2cTYA5E
Specifically Yours, Eric Morgan