Hi Adrian,
Would you be able to suggest any metrics from which you consider this forum to be definitely successful or a definite failure? For example, if the current level of non-engagement persists for x weeks or months, when would this be considered a failure? Meta engagement (talking about the forum itself) doesn't count :).
For example, I clicked on the emailed update, could see the message, tried to reply but had to login again and then had to go back to the email and click on the link again, instead of just replying to the email.
It seems that a facebook group is the usual approach taken, despite the reputation of that august institution as a facebook group is as simple to use as the original list server.