SMTP proxy/smarthost

[smay]

We provide email hosting for several companies with their own Exchange server (generally on SBS.) They use one of two mechanisms to receive email:

1. Exchange's POP3 connector. Pros: email is buffered and spam-filtered. Con: there's up to a 15 minute delay in receiving it.

2. Have an MX record pointing to the Exchange server (with firewall port forwarding, etc, etc) and receive it directly. Pro: mail is received instantly. Cons: it's not buffered or spam-filtered.

Is there's a solution that combines the pro's of these two? Some sort of SMTP proxy/smarthost arrangement perhaps?

 

[will-lo]

you can turn a DA box to a anti-spam/virus gateway like messagelabs.com (by pointing the domain MX to the DA box IP), however it requires significant change to exim and some custom scripting.

 

[floyd]

1. Exchange's POP3 connector. Pros: email is buffered and spam-filtered.

If this is business email then this is definitely a con. Email should be accepted or rejected but never filtered. If the email is filtered what do you do with it? You can't bounce it back to the sender because the From address is probably fake so with any false positives the sender will never know that it was filtered and assume you are ignoring the email when you don't reply to it. If you look at the filtered email well then that just defeats the purpose of filtering.