Here's a run down on setting up Postini with IMail. Really quick...disclaimer in case of error but here are my notes...
Postini
You probably all run some kind of mail software with spam blocking capabilities. However the painful thing is that spammers are out there inserting mail directly into your mail server and overloading spam boxes all the time. This takes up resources on your mail server(s) and clients.
What's kind of neat about Postini is that it's a filtering service in front of your mail server. You can force all inbound and outbound mail to go through Postini if you have your own mail server or a service that offers Postini. By setting up Postini correctly a lot of the garbage bombarding your server can be stopped before it ever gets that far.
Postini was bought out by Google and as you can imagine has a tad bit more mail to analyze than the average company hosting an email system. By passing all the garbage through them first, I would hope they can do some pretty good analytics on mail going through their system and figure out how to weed out the junk, the same way they figure out how to put the best web sites at the top of the search engine results [hopefully!]
Postini blocks viruses, spam and has a bunch of cool features like allowing you to block IP ranges from sending mail to your server. Since a lot of spam comes from certain parts of the world, if you don't do business in those areas you can simply block out entire spam friendly networks completely. I found that blocking out everything but ARIN significantly reduced my spam on a particularly old domain that is probably in every spammer's list in existence.
The other cool thing about Postini is that it allows you to force TLS between two parties - for regulatory copmliance or simply because you want to know your email transmission is encrypted end to end (which can be hard to do).
These are just a few of the highlights of Postini service.
The biggest problem with Postini is that, if you're a small business, getting support is challenging. You don't always get answers and when you do they are vague or not actually answering the question you asked or simply don't resolve the problem. Lately, however, I haven't had a ton of questions which is good. The service has been pretty reliable.
IMail
If you're not interested in spending mega-bucks on Exchange, IMail is a simpler, less expensive option and the company provides very good support. When it comes to email that's important to me because I find email to be a royal pain. As noted in a recent episode of American Greed, spam is the backbone of organized Internet crime. They are all trying to get into your in box to get you to click a link - or something.
When people's email isn't working - they want it fixed. Now. Although I'm pretty handy with Java, open source typically comes with no or minimal support. Additionally open source has so many people contributing that are not quite held accountable in the same way I would expect a company with paid staff to be. Mostly, I'd rather pay a bit more and get someone who can help me fix things fast than futz around with user groups and mailing lists or reverse engineering code to find a fix to a type of technology I find completely annoying because it is hard to secure, unreliable and always under attack. I prefer to deal with email as little as possible. I just want to call someone and get an answer. There is one person at Ipswitch in particular I have talked to over the years who is extremely knowledgeable about IMail and was able to quickly answer all my questions during set up.
For me running on IIS was kind of a pain because I prefer Java and it's another thing to manage, but I've used Imail in the past and it's reliable with good support as mentioned. For those who like and know IIS this would be a plus. Setting up the SSL cert was much easier with IIS than Java. The web site runs a little slow but going to look into how that can be tweaked. Using IMail is, for the most part, a piece of cake. The only thing I found challenging (having a basic understanding of mail servers) was getting the SSL cert installed and finding all the parts and pieces to make it work with Postini.
Set Up
--IMAIL--
> Purchase or get trial at IPSwitch.com
> Install - call for help as needed.
> Note that MX records will be pointed at Postini (see below) not your mail server.
--POSTINI--
> Set up an account and login to the System Administrator
> Click on the Orgs & Users tab
> Select your top level account from the drop down list of orgs
> Click the link (name) of your account (top node in the list)
> Enter a new org name in the box at the top and click the "add" button
> Click on orgs & users tab to get the full list of orgs
> Click on the name of the org you just created to view the settings.
> Click on the "general settings" link 3/4 down the page
> Change "email config type org" to Yes and save [allows mail server settings for this org]
> Click on "DNS Instructions" for MX records to use...
--EDIT YOUR DNS--
> edit your MX records to include the specified servers (note that each domain should have the domainname itself in the MX record - replace the part that says yourdomain with the domain for which you are setting up email)
--POSTINI--
> Click on "domains" under the tabs and add a domain
> Click on "users" under the tabs and createa user
> Click on "Inbound Servers" tab, "Delivery Manager", then "Edit" to add your mail servers. If you have your own mail server choose "Use my own mail server" and % to balance load to each server.
> There are other cool features you can look into later...manually block mail from certain IPs (bottom right when you click on "Inbound Servers"), force TLS between certain domains, etc.
--IMAIL--
> In your mail server allow relay from Postini (ONLY so you don't create an open relay for spammers!) In the latest version of Imail you would click on "Services" on the left, then double click on "Imail SMTP service".
> Under "General" click on the "Addresses" tab. Select "Group" from the drop down and enter the Postini IP addresses specified for your outbound mail configuration. The IP addresses depend on which server number you were assigned when you signed up for the service. The server number is in your MX records specified in the DNS instructions. More in this document:
Postini Outbound Services
--POSTINI--
> Click on "Outbound Servers" tab, and at the bottom left choose "Add Another Outbound Email Server" and add your mail server(s) that will be used for sending bounces back to your users.
--IMAIL --
> Set up webmail per the IMail instructions.
> If you want webmail to show up on it's own domain with no directory at the end and no access to the administrator and other things from that domain, set up a second web site on IIS and point it specifically at the webmail folder instead of the parent directory. In other words instead of mail.mydomain.com/web_mail_folder to get to mail you point IIS web site at the web_mail_folder and then can get to that same thing by going to mail.mydomain.com (if that doesn't make sense...call IPSwitch. They are very helpful.)
-- SSL CERTIFICATE (webmail and mail traffic) --
> In IIS create a cert request. I used Digicert.com and they were extremely easy to work with. Click on the IIS link on the left side of their home page and scroll to the bottom to get instructions for IIS cert request.
> When you get back the certificate, install it in IIS (for the domain you're running webmail on).
> Test your webmail domain and make sure it's accessible via SSL (https://mail.mydomain.com)
> For Digicert there were some chained certificates I needed to install in IMail. Originally exporting from IIS didn't work because the output didn't include the full chain. So...
> Use the MMC to export the cert with the full chain of certs:
http://www.digicert.com/ssl-support/pfx-import-export-iis-7.htm
> These "unsupported" instructions will get you two files that have the private key and the cert in separate files - I don't know if there's any issue with this...but I did it and it worked.
http://kb.imailserver.com/cgi-bin/imail.cfg/php/enduser/std_adp.php?p_faqid=42&p_created=1218038946
> You'll need the full chain in your cert file as explained in this article:
http://support.ipswitch.com/kb/IM-20010425-DM01.htm
-- PORTS AND FIREWALL--
> You'll want to make sure spammers can't inject mail straight into your mail server, so set up your firewall to only allow SMTP to Postini
> In order to let users connect, you set up a separate port for them to connect to and force authentication on that port. In Imail there's an option to do this on the "advanced" link for SMTP server settings.
> I also tried to use that same port for SSL hoping all traffic would be SSL encrypted on that alternate port but found the following info at the bottom of this link:
http://support.ipswitch.com/kb/IM-20050428-DM01.htm
Note for Outlook and Outlook Express users: If you tell your client to use SSL over SMTP and set the port to anything other than 25 the client will attempt to negotiate the SSL connection before sending the EHLO as if it was communicating over a dedicated SSL port. This will not work on the extra port. Users must issue EHLO and then STARTTLS to use SSL over the alternate SMTP port.
When users tried to enter the port and check "SSL" in outlook didn't work. They had to uncheck it to get this to work. However another mail connection I used from an alternate piece of software didn't work. By moving SSL to a separate port I believe that Outlook will attempt to use TLS if available. What I wonder is - what if something happens and it's not? The problem here is that with Postini you can force TLS between your mail server and Postini and between Postini and other mail servers, but for people connecting from their machine to our mail server - we also want to make sure that portion of the transmission is encrypted. Need to set up some alternate type of monitoring to enforce this potentially.
> So for now users are set up to connect to alternate port with SSL unchecked.
> Set up SSL port for POP/IMAP also and provided that port with "server requires SSL" setting.
TLS is cool because it runs on the same port as SMTP so takes up less ports, easier for users to configure and uses TLS when available otherwise not - but for connections from users to the mail server, wondering how that can be enforced and monitored as noted.
-- DICTIONARY ATTACKS --
Shortly after set up we were plagued by "dictionary attacks" (see my twitter account for more on that http://twitter.com/teriradichel
To prevent or at least slow down dictionary attacks - where someone just hits your web server with every possible valid email they can think of in rapid succession until they find a good one - edit SMTP service settings in the box that says "Dictionary" attacks and limit the number of attacks per session, failures, etc.
-- TRANSFERING MAIL TO MAIL SERVER --
If you're transferring users from another mail server you might also be interested in:
How to transfer your users and mail from your old mail server to new:
http://kb.imailserver.com/cgi-bin/imail.cfg/php/enduser/std_adp.php?p_faqid=716&p_created=1247145176&p_sid=gOAbiCfk&p_accessibility=0&p_redirect=&p_lva=&p_sp=cF9zcmNoPTEmcF9zb3J0X2J5PWRmbHQ6MSZwX2dyaWRzb3J0PSZwX3Jvd19jbnQ9MTU4LDE1OCZwX3Byb2RzPTAmcF9jYXRzPTAmcF9wdj0mcF9jdj0mcF9zZWFyY2hfdHlwZT1hbnN3ZXJzLnNlYXJjaF9ubCZwX3BhZ2U9MiZwX3NlYXJjaF90ZXh0PW1vdmUgbWFpbA**&p_li=&p_topview=1
Basically to move mail you transfer all your users over as noted above. Then you can connect via IMAP in outlook to both mail servers, and copy all the mail from the inbox of one server to the inbox of the other. There may be other folders to copy as well depending on what the user has set up.
Probably missing a few things here but that's the gist of it.
