I unsubscribed from renewal notices for getpublished.xyz and wanted to resubscribe. The forum tells me the only way to do this is to update the email address, which I just did. How can I know if I'm subscribed again? (I just added "+getpublished" to the previous email address.) I'm running Dokku so I'm actually not 100 % sure what certbot command was run, as I only see the buildpack output.
Welcome to the Let's Encrypt Community 
To the best of my knowledge, you will only be notified if renewal is due or revocation has occurred. There isn't a sign-up/update "confirmation". I think I'll submit an issue against Boulder (the Let's Encrypt CA software) to try to push this forward. It has been a somewhat regular question and annoyance.
The ability to simply resubscribe would be nice too 
I concur. Issue submitted.