[qmailtoaster] backscatter

[slamp slamp]

hey guys, can anyone shed light on my dilemma please.

i have one toaster which is the primary mx. i have an account with rollernet for their free backup mx. so whenever my primary is down, the backup will take over then deliver them to my primary when it is up. the problem is some e-mails are rejected due to its spam nature then this bounces to rollernet which doesn't like this because they are getting e-mails they did not send. how do i prevent this from happening? of course i still want spam filtering. do i just put rollernet to spamassassin whitelist? its kinda hard to test since testing means i would have to take down my toaster.

Thanks in advance.