Email server logs typically record every connection to the server - who connected, when, from which IP address, and what they did. Mail transfer logs record sender and recipient addresses, message sizes, delivery status, and timestamps. Authentication logs record login attempts with usernames and source IPs. Together, these logs create a comprehensive record of your email activity that reveals who you communicate with, when, and how often.
These logs are the first thing requested in a legal investigation, the first thing targeted in a security breach, and the first thing analyzed in a surveillance program. Even if the content of your email is encrypted, metadata from logs can reveal your communication patterns, contact network, and activity schedule - information that is often more valuable to an adversary than message content.
The only way to protect against log-based surveillance and investigation is to ensure that logs do not exist. AnubizHost no-log email hosting is configured to prevent log generation rather than relying on log deletion, which is always less reliable and leaves forensic traces.