The custom email prefix feature lets users personalize the username part of a temporary email (e.g., yourname@domain.com). To set it up: 1) Visit a temp-mail service and locate the "Custom Prefix" option; 2) Enter a desired prefix (e.g., netflix2024), generating a full address (e.g., netflix2024@tempbox.net); 3) Use it for registrations. Key benefits: Organization: Assign unique prefixes per platform (e.g., amazon@xxx.com). Memorability: Replace random strings with readable names. Tracking: Identify spam sources easily. Some services allow prefix reuse or password protection for added security.