Mailing list mode user not getting emails and not appearing in skipped_email_logs

We have a user who is set for mailing list mode but still doesn’t get some emails. The email notification for the post/topic doesn’t appear in the email_logs table for them NOR does it appear in the skipped_email_logs table for their user_id.

So far, they’ve only mentioned missing emails one category, but they DO get some email notices from that category. Other users on the same email domain get the notices.

We’re not exactly sure when this started, but they did change their username years ago, so I thought it might be this issue, but it seems that in the end that wasn’t traced to a username change.

I checked /logs too. Any other suggestions for logs we might look at to see why Discourse isn’t generating some email notices for them?