The main method is to stop spam being sent from your IPs in the fist place. We have a number of mechanisms:

- Automated outgoing spam filters (via rspamd) to prevent obvious spam emails

- Enforced DKIM validation on all accounts

- Automated / manual review of sudden outgoing email spikes

- Automated bounce response management

- Automatic block lists for any emails that hard bounce

- No free plan

- Manual review of new accounts

Additionally behaving as a legit sender helps, so things like greylisting, the right encryption support, rDNS records etc all need to be in place.

We also monitor the public block lists and take action if our IPs are mistakenly added to them