The mailing list for listmasters using Sympa

[address@concealed]

I understand what permanent and temporary bounces are, however sometimes the 
type field is blank, which I think means the server didn't respond with any 
useful information. I have noticed that some are listed as "success", usually 
all from the same domain, both AOL and netscape.com email addresses are doing 
this.

Can anyone confirm why some are blank, and some are success?

Any help appreciated,
Jayson Strudwick