Additional IP for customer and malware SPAM

[Spacedust]

If each user will have it's own IP will this prevent main IP server from getting on DNSBL lists ?

Example main IP is 150.254.10.10, customer IP is 150.254.10.20.

Then user is getting hacked and someone is sending mail via his account. Will they be sent via 150.254.10.20 or 150.254.10.10 ?

[MRatWork]

IP sender is __base__ in 'A record' for each domains.

[Spacedust]

IP sender is __base__ in 'A record' for each domains.

Good - that's what I need So it's safe to assign such problematic customers a dedicated IP and let them be blocked on DNSBL without affecting main server IP and all other customers using it.