Hi,

I am in the process of setting up a email solution. One of my few outstanding tasks is to get the mail server to automatically zip/unzip any zip files.

I am running PostFix (Maildir), Courier-IMAP and Spamasssassin. I need the email server to automatically zip any outgoing attachments and unzip any incoming. What is the best way to accomplish this?



Many thanks

Fredrik

Unzipping incoming attachments shouldn't be hard, could do that with a procmail recipe. The problem is attaching it back on if the client expects anything else than plain text e-mail. Why would anyone want *outgoing* attachments to be zipped automagically? If it's due to batch sending you could make a script that compresses attachments and send it with 'mpack'? Not that it's not possible. The method should be somewhat the same as for those that require their outbound traffic to have a "disclaimer" attached, a LQ search should show some threads about that.

The plan is that this email server is going to act as a relay for several other servers. The other servers will have extremely little/slow and expensive internet connectivity. I have therefore been looking at compression to make the system more efficient.

The other servers are all running Exchange were I found a plugin for which can automatically zip outgoing emails and unzip incoming. The ide is to have something like this, email arrives at Linux server, all attachments get zipped, email is then collected via pop3 from the Exchange server when internet access is available and then automatically gets unzipped again. This would work the same for outgoing emails as well, meaning you get compression and the user would never even know that the attachments had been zipped.

To be honest I am not familior with procmail but I will look into this now.

Thanks!

Testing the right procmail recipe will be the least of your problems, compatibility with non-plain text MUA's could be. Maybe get ideas from TNEFclean or Sanitizer or similar.

A very compelling reason to zip attachments is when your users like to send 15MB excel files and have to authority to override a decision to only allow 4MB attachments. Those 15MB excel files will zip down to 2MB. This is much better! Some mobile users have aircards and a 15MB email will effectively take thier email down for 30 minutes.

on that subject, anyone figured out how to automatically zip attachments?

I never figured this out, the project got put on hold as I had other stuff to deal with but I do plan to revisit this someday. I didnt have a good testing environment to test procmail with as my main server was already up and being used by clients.

Let me know if you have any luck and I will try the same when I get time.