Recipient id's, not email addresses. From the small number it's likely some recipients were naturally deleted and later recreated, though you should still check your ETL jobs to make sure they're upserting recipients and not doing anything off-spec. This will sound unorthodox, but to fix the existing issue all you have to do is update the recipient id's in nms:recipient to match what's in nms:trackingLogRcp, i.e. `update nmsrecipient n set n.irecipientid=t.irecipientid from (select irecipientid from nmstrackinglogrcp where semail=n.semail and noyolo) t`. NB I wrote this in the comment box here to help clarify, don't copy-paste this to your prod db, dogs and cats living together, etc.