My apologies for the recent spate of problems. I think I’ve narrowed the problem down to the /m/fediverse and /m/random magazines. For some reason, mbin is generating an enormous amount of outbound delivery messages for these two magazines. I first tried removing the hashtags from /m/fedivese, but that was only a quick fix. So I deleted the magazine. (Note, the notifications appear to be related to the “microblog” function, and were originating from accounts on lots of mastodon instances, so I think there is a bug somewhere).
I noticed /m/random doing something similar. I have removed all the subscribers from that magazine to try to reduce the number of notifications it is sending. I don’t know if that will help - I have a feeling the instance can’t keep up with that happening in both random and fediverse.
Anyhow, the queues are draining fast now. I purged about 600000 queued delivery messages that (based on a random sample) all appeared to be associated with fediverse and random. That should let the rest of whatever is backed up get moving again. and hopefully stay moving.