Should Out of Office be sent externally?

There is an option in Exchange System Manager to prevent or allow Out of Office messages to be sent to external addresses. Technically, this is pretty easy to configure - and Exchange 2007+ lets you set a different message for internal and external use - but the question I have today is whether it's a good idea.

My manager asked what is "best practice" on this. I think the answer is that there are arguments both ways and have detailed some to him, but I suspect there are other reasons that I haven't yet thought of.

I'll create two answers; one for "yes, let people do it" and the other for "no, no, no, this is a terrible idea" and put in the reasons I can think of. Can I ask other people to edit in any more arguments they can think of?


Yes, it should be sent externally.

  1. The sender of an email to a business address, often a customer, has a reasonable expectation that they should get a timely reply; getting an OOO message gives them a warning to adjust their expectation.

No, it should not be sent externally

  1. If a spam is sent from forged sender address, the unfortunate forgee gets deluged by OOO messages.
  2. OOO messages should not be sent to mailing lists, in reply to email newsletters, etc. (a rule that prevents OOO replies to Precedence: Bulk can resolve this).
  3. OOO messages can give criminal social engineers useful information on who is out of the office - they can pretend to be someone from another office who is actually on holiday as they don't risk meeting the person they are impersonating.
  4. OOO messages can give out information you don't want to give out to the general public, eg mobile phone numbers.
  5. For employees in "groups" (like support), customers shouldn't be contacting them directly anyway - they should be going through the group PDL or ticketing system: the exact tech who works with them should be irrelevant.
  6. Any personal or legitimate business contacts who must know you're going to be OOO should get a personal email from you, not an automated responder.