Subscribed addresses for email undeliverables not in the subscriber database

[rjsob]

I am receiving non-delivery/undeliverable notifications for several email addresses. I check the subscriber database for those email addresses and they aren't listed. I exported the entire subscriber list and did a search in that file and the email addresses are not there. They are not listed as deactivated, paused or active. Yet each day when the emails go out to subscribers, I get the same non-delivery notifications.

I know that Feedburner is supposed to deactive addresses after 5 delivery failures, but I continue to get the NDRs well past the limit of 5. And these are not "out of office" or automatic replies, they are delivery failures for email addresses that are no long valid.

Again, a full search of the subscriber list doesn't show these addresses.