Email virus/spam scanning (Messagelabs)

One of our customers is having a bit of trouble with loads of viruses and spam via email, their exchange server (PIII 1GHz) does have anti-virus on it but it is taking its toll on the box. We have been in touch with Messagelabs and their prices are a bit too high for our customer (only a small business) what we would like to do is set up our own "Messagelabs" if you catch my drift. I know this will comprimise of a SMTP server (postfix/sendmail?) and anti-virus & anti-spam (ClamAV & SpamAssassin?) but I dont quite know how to configure it.

What we would like for is this server hosted at our site to recieve their emails, scan and clean them and automatically forward them on to their exchange box - how would I set this up?

Cheers,

Craig

I would assume that you would have to repoint their existing MX records to your new mailserver first and foremost... Then reconfigure their Exchange server to talk to your new mailserver and pickup their email from a global account e.g. postmaster account (mailbag/mailbox domain). Possibly you could also do it by setting the Exchange server to relay through the new box...?

Having said that, I have a feeling that you may not be able to get Exchange to pickup from a mailbag / mailbox domain..? In which case you would need something like Vpop3 or Argosoft Mail Server Pro for the customers old mail server...

Bear in mind that message labs use multiple AV scanner engines and probably a whole load of custom filters. You will need to run at least one AV scanner and be fairly strict about rules as well if you hope to even vaguely emulate that kind of service... It would be an idea to create a list of their trusted domains (whitelist) and if they receive a lot of spam from certain domains, a blacklist.

indeed the reason messagelabs get away with the price is because of how difficult the task is.

You could look at someone like sophos, they provide both AV + AntiSpam from the one vendor. But its not cheap (however its probably not much more than you current AV costs).

Thanks for the replies guys :) I understand we wont be able to offer the kind of scanning Messagelabs does, but we would like to take some load off our customers server (we have a few servers with little on them..) and then pass on nice and clean messages to them (If one or two get through it dosent really matter - they will still have their AV on the exchange server) I understand exchange et all, I just dont know how to make a SMTP server scan/clean the message and then forward it to our customer.

Craig

[Edit] I am after a free solution - If there is a cheap/free windows solution then all the better - linux will be fine though :)

A clark connect box running in gateway mode will relay mails in this way. You need more than just an SMTP server like sendmail to be configured , you'll want some form of MTA to actually relay the mails once they have been processed by your AV/ Content Filter

I *used* to like message labs , but I'm not a big fan of their MD or the fact that their SLA for message processing isn't very good. There are alternatives.

Hexus's very own host fluent can provide mail forwarding with AV / Antispam for a pretty reasonable cost.

There is a service in a smiilar scale to messagelabs , which is faster and cheaper provided by a company called Postini which you may also want to look at.

Omniquad also have a similar service to Messagelabs at a more reasonable price. Might also be worth talking to them to see how much it would be.