use rdns, spf and dkms, luke.

... and sign up and monitor every FBL you can get your hands on, have outgoing spam filtering gateways, procedures to rotate subnets in case Microsoft/Outlook/Hotmail receive a single complaint about any message relayed by your MTA and take their sweet time "conditionally mitigating" you. Pray daily that none of your users get their email creds stolen on a coffee shop wi-fi.

It's a very lame part-time job.

you won't got onto a FBL if you are the only sender.