Inboxtrail is an email deliverability tool that helps organizations manage email deliverability by providing a platform to test and analyze deliverability rates, identify issues, and improve inbox placement. The company was created to address the lack of transparency in email deliverability, which can be complex and difficult for many businesses to understand. Inboxtrail's ESP Comparison Center provides daily delivery tests from various ESPs, publishing data that helps users gauge their email deliverability. The tool measures deliverability across top ISPs, including Gmail, Hotmail/Outlook, Yahoo, and AOL, and also tracks differences between marketing emails and transactional emails. Deliverability issues are more common with Hotmail and AOL, but can be mitigated by modifying content or waiting a few days to see if the problem improves on its own. Inboxtrail recommends using shared IPs for sending transactional email due to their ease of management and lower risk of IP reputation issues. The company also plans to expand its ESP Center to include analysis of other metrics such as speed, quality control, integrations, and customer support.