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Possible Duplicate:
Vacation Response Loop

What would happen if you sent an email to someone, who has an out-of-office auto-response set up, while you yourself also have an out-of-office auto-response set up.

Would this create an infinite loop and crash the email server?

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marked as duplicate by n0pe, Hello71, ChrisF, Ƭᴇcʜιᴇ007, Mehper C. Palavuzlar Jul 27 '11 at 17:00

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

I moved my answer to the duplicate question, but the answer is that e-mail servers use the message id to prevent this from happening. – KCotreau Jul 27 '11 at 15:36
up vote 2 down vote accepted

Unlikely. Most Out-of-office alerts will only send one alert per sending address per day / week, so in your example your recipient would send you and out of office alert, which would trigger your system to send them an alert. Your recipient would then not send any further alert back to you, so no loop is created.

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Yes, it is possible. An infinite loop would be created until the mailbox is full. I'm not sure if email providers are clever enough to detect this, but some of them might start categorizing the newer emails as spam.


I only found a few examples online and they seem to be an year to two years old. Maybe the new email providers do check this.

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It's rare to encounter these anymore. Email Server developers caught on a long long time ago. The biggest problem MX servers see these days is bloated Inbox. . . Grrrrrr. – surfasb Jul 27 '11 at 15:57
@surfasb: Properly designed mail servers shouldn't have problems with the inbox size -- they just append a new message and that's it. – grawity Jul 27 '11 at 16:44
Oh, it's not the text messages we have a problem with. It's the attachments and well, the old emails. But that's how the boss wants it. One gargantuous inbox. . . with unlimited size attachments. We secretly cap it and archive the old emails though, shhhh. No one has caught on yet. . . – surfasb Jul 27 '11 at 20:10

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