With the increase in volume on my List ([log in to unmask]) I have finally decided to activate some automatic removal of faulty addresses (I previously had Auto-Delete-No in my header). I have thus recently set Auto-Delete= Yes,Semi-Auto,Delay(10),Max(100),Probe(30) (I decided to set delay to 10 simply to make sure that users whose systems may go down for a while are not inadvertantly removed.) However - and I admit I'm having a "thick-day" today by the way - whilst I think I understand the first 4 components of this command I'm having a little trouble really understanding what assive probing is all about. Basically what does passive probing actually do, and will it assist in auto-deletion or does it do something else ? I'm also a little confused with the manual which says that probe(30) is a default value for lists <1-2K - and to switch it off requires probe(0) in the header. Is this saying that probe(30) will be active if I have it in my header line (as above) and it will also be active if I delete the probe= component from the auot-delete command altogether, and that the only way to switch it off is to include probe(0) ? Hoping someone can help. Thanks in advance. Peter R