Expensive ESPs: Some ESPs charge higher rates for features you may not need. Always evaluate if the features offered align with your business needs. Poor List Management: Sending emails to unengaged or inactive subscribers can increase costs without yielding results. Non-optimized Campaigns: Failing to A/B test or personalize your emails can lead to lower conversion rates, making your spend less effective. High Bounce Rates: Not maintaining a clean email list can result in high bounce rates, which can increase costs and damage your sender reputation.