To prevent issues, it should be clearly stated that the "reply-to" address option doesn't always work for out-of-office automatic responses. It is apparently entirely up to the end-user's email admin as to whether the reply-to or from address is used. After speaking to customer service, it seems this is a known issue with Constant Contact, but there's nothing about it in any of the documentation or support. I suggest adding a Pop-up warning about this if the "Use a different address for replies" option is selected. Our EVP did not appreciate receiving thousands of OOO responses on her phone after an email was sent to every contact we have in Constant Contact.