The technical specification for electronic mail defines a limit on the length of the recipient and sender address fields. This limitation is typically interpreted as the maximum number of characters permitted in the local-part (before the “@” symbol), the domain part (after the “@” symbol), and the entire address combined. For example, specifications might dictate that the complete address not exceed 254 characters, with constraints placed on the components before and after the “@” symbol.
Adhering to address length restrictions is crucial for interoperability between different email systems. Compliance ensures that messages can be routed and processed correctly across various servers and clients. Historically, these limits have been established to optimize resource allocation and prevent potential abuse, such as denial-of-service attacks that exploit excessive data lengths. These size constraints can improve the reliability and efficiency of email communication worldwide.