A mail server is an application responsible for sending, receiving, and storing email. It operates using protocols like SMTP (for sending) and IMAP or POP3 (for receiving), facilitating communication between users and their email clients. When an email is dispatched, the mail server processes it and ensures it is routed correctly to the intended recipient's server. Mail servers also manage attachments, provide spam filtering, and enforce security measures to protect sensitive data. Overall, they enable reliable and efficient electronic communication.