Five ways to cut your complaint rate below 0.1%

Gmail acts on a 0.3% complaint rate; aim for under 0.1%.

• Only send to people who opted in.
• Set clear expectations at sign-up.
• Make the unsubscribe link obvious — an easy unsubscribe beats a spam complaint.
• Honour unsubscribes immediately (suppress the address).
• Prune unengaged recipients regularly.