Francoise, a few questions about passive probing: You said that it uses a lot of resources since it sends a separate message for each recipient. I thought messages posted to the list doubled as probes so that those subscribers with good addresses would not see a "probe" message. Even if you did send a separate probe message for each recipient, why does this use up so many resources versus a regular posting to the list, is it the processing on the server? It appears to me that the number used in the header, Probe(#), corresponds in a way to a list with one posting daily. For example, you say that Probe (10) will check 10% of the list. The manual says that the number specifies the number of days between probes for a subscriber. Obviously, with my list with monthly postings, the number of days between probes would be much more than 10. However, if my list had one message posted daily Probe (10) would allow for 10 days between probes. Can you please confirm my understanding. Also, can you confirm that Passive Probing works the same as Active Probing once a bounce is received, i.e. from the manual: "LISTSERV first sends the PROBE2 template with a copy of the bounce, to show the user (if the account actually works in spite of the bounce) what garbage his mail system is sending people. LISTSERV then schedules a new probe for the next day, or deletes the user immediately, depending on the auto-delete policy. Every failure triggers a new daily probe until the user gets deleted or the problem gets fixed." Thanks!