resending

Resending refers to the act of sending a communication or data more than once, typically after the initial attempt failed or a new recipient is involved. In digital communications, resending is a mechanism to improve delivery reliability and ensure receipt. The term applies to electronic mail, instant messaging, push notifications, and data networks, as well as to physical or informational materials that may be reissued.

In electronic mail and instant messaging, servers and clients typically retry undelivered messages. They may apply backoff schedules, limit the number of attempts, and space retries to reduce network load. Duplicates can occur, so systems often implement deduplication or idempotent handling, ensuring that repeated delivery does not lead to unintended side effects.

In data networks, retransmission is a fundamental concept. Protocols such as TCP automatically retransmit packets when acknowledgments are not received or timeouts occur, while UDP-based protocols rely on applications to decide when to resend. Resending schemes balance reliability with network congestion and latency considerations.

In postal or physical delivery, resending generally means reissuing mail or parcels after a return to sender, incorrect address, or non-delivery. Organizations may update addresses and attempt delivery again, and customers may request resending of documents or notices.

Considerations and best practices include using unique identifiers to detect duplicates, implementing idempotent operations, and controlling retry behavior through backoff and limits to avoid congestion. Clear communication with recipients about resends and adherence to privacy rules when repeating sensitive content are also important.