Email loop

An e-mail loop is an infinite loop phenomenon, resulting from mail servers, scripts, or e-mail clients that generate automatic replies or responses. If one such automatic response triggers another automatic response on the other side, an e-mail loop is created. The process can continue until one mailbox is full or reaches its mail sending limit. In some cases, the e-mail loop could last an infinite duration. E-mail loops may be caused accidentally or maliciously, causing denial of service. Although rare, e-mail loops involving more than two participants can also occur.

E-mail loops are not as common today as in the past, due to changes to e-mail software, both on the client side and the server side, that prevent automatic replies to vacation responses and bounced mail responses.

Costs of an e-mail loop

• Bandwidth: E-mail loops use up limited bandwidth over networks.
• Processing time: E-mail loops will take up processing time, and could slow down other processes.
• Disk space: Automatic e-mails are usually stored in the mailboxes of participants.
• Human Time: Network administrators may have to intervene to fix the problem, or clean up mailboxes. Also the mailbox user/owner will have to delete the numerous responses in order to clean up their mailbox.

Causes

• Autoresponders, such as automatic "on vacation" replies
• E-mail bounces due to, for example, exceeding the inbox disk quota
• Replies to indicate that that mail has been delivered
• Replies to e-mail read-receipts

External links

• Vacation E-Mail Loop
• The Free Dictionary
• Mail Loop Error
• RFC 2919