Recommendation for easy to use autoresponse

Hi, I have been looking around and found some solutions for virtual users. In my case, I have a mixture of virtual and local user accounts. I want to be able to customise the response for each user. Is there any autoresponse add-ons that I can use?

conversation with gmail-smtp-in.l.google.com timed out while sending end of data

I can send short emails (1KB) from my mailserver (abc.domain.com) to gmail account (t...@gmail.com), but for larger emails (7KB), it fails. It gets deferred on the mail queue forever. But this same mail can be sent to yahoo. Am I missing something?