Deploying Suse Linux Enterprise Server
 |
Purchase "Deploying Suse Linux Enterprise Server" at Lulu.com |
Implementing Mail Services
- Configuring the Mail Server
- Enabling Spam & Virus Protection, Using Fetchmail
- Enabling Mail for Users and Groups, Advanced Configurations
Configuring the Mail Server
The first step in configuring your server to handle mail is the process of installing the software. Normally I wouldn't cover this obvious process, however in this case you will be presented with an error that will provide to you a few options. So, in order to install the mail server software, open the Yast Software Management module and change the "filter" to Patterns. Now simply select the "Mail and News Server" Primary Function.
You will probably be prompted with an "error" stating that yast-mail conflicts with other resolvables. What this means is that you cannot have the "Yast Mail" module and the "Yast Mail Server" module installed at the same time on the server. To continue to install the mail server software simply check "Delete yast2-mail" and hit "OK - Try Again".
Once all of the software is installed, go ahead and launch the Yast Mail Server module. Upon startup it will check for all of the required software and ensure that LDAP support is available. If you haven't already done so, it will inform you to configure the DNS server with LDAP support. If this is the case, refer to the DNS Server chapter of this book to configure this service properly.
Mail Server Domains and General Configuration
The Yast Mail Server module is split into different sections or tabs that are separated by their functions. I will try to give a thorough explanation of all of these sections and give you information on what needs to be done in order for the mail server to work properly.
First, lets look at the last "tab" in the list, the Mailserver Domains. This section allows you to specify all of the domains that your mail server will deliver and receive mail for. When you "Add" or "Change" these Domains you can configure them into different "types", including:
- main - When set, all users will receive emails from this domain using their username.
- virtual - When set, only users that are assigned email addresses through the Yast User Management Module will receive email for this domain.
- local - When set, all users will be able to receive email.
- none - If this is set, the mail server will not receive mail for this domain.
Also, when you create or edit these domains, the masquerading option gives you the ability to change the outgoing email address or the outgoing mail server for that domain (useful under certain circumstances). Just remember that you will probably want to create a separate DNS Zone for any domain that you want to receive mail for.
The Yast Mail Server Module's Global Settings and Managing the Domains to Receive Mail
Now let's move on to the "Global Settings" section of the Yast Mail Server Module. This section allows you to adjust the Server Identification, the Mail Size limit and how Outgoing Emails are handled. The settings that you can adjust here include:
- Server Identification - Under most circumstances you will not want or need to adjust the Server Identification.
- Mail Size - This allows you to limit the size of mail that your server will handle. This will vary upon your environment and what you will use your mail server for. If you are utilizing your mail server over the Internet, it is courteous to limit the size to at most 10MB.
- Outgoing Mails - This section configures how your server will deliver mail outside of your network over the Internet. If you are simply using this server for internal mail select "No Outgoing Mail". If you need to utilize your ISPs, or another mail server on your network to deliver outgoing mail, select "Use Relay Host" and enter all the required information. Otherwise, simply use "Direct Delivery".
Mail Storage and Delivery
The "Local Delivery" section allows you to specify how you want all of the mail to be handled, such as utilizing a separate service to store emails, using the filesystem for mail storage, or even specify that all mail be sorted and delivered with procmail.
Under most circumstances, you simply need to decide on whether or not to use the filesystem, or use Cyrus IMAP for mail storage. If your network only uses GNU/Linux or other Unix type Operating Systems (and you do not need remote access to your email), the filesystem option becomes viable (especially when storing the mail in the user's home directory). However if you have Microsoft Windows Clients and/or you want to be able to access your mail remotely (either through POP or IMAP), you must use the Cyrus IMAP "Local Delivery Type".
When setting up Cyrus IMAP you are presented with a few options regarding security, mailbox size and Idle Time limits for Clients. In regards to the security option, this allows you to require all communication to the server be encrypted - highly recommended for any business.
The Mailbox size options give you the opportunity to limit the size of your user's mail storage. If you set a default mailbox size, the server will notify the user when the mailbox reaches the "Quota Warning Limit" percentage. This will allow the user to know that they may want to clean up their mail a little bit. When setting Quota Limits, normally the server will still deliver mail well beyond the quota limit unless you check the "Hard Quota Limit" box. When this box is checked the server will reject any further messages for that user (use with caution).
Setting the Local Delivery to Filesystem and to Utilize Cyrus IMAP
Other options on this page include "Fallback Mailbox" and "Use Alternate Namespace". The fallback mailbox allows you to specify a local mailbox that all messages to non-existent accounts will be delivered to. The "Use Alternate Namespace" option allows you specify how the user's additional mail folders are located. When checked, they are located on the same level as the INBOX folder, and when not checked, they are listed as sub-folders to their INBOX folder.
Mail Server Relaying and Communication Between Servers
Once you configure how to store all of your email, you now need to focus on another function of a Mail Server - Mail Delivery. Suse Linux Enterprise Server utilizes the postfix MTA (Mail Transfer Agent) and fortunately, by default, Postfix is a very secure MTA. Although, even the most secure services can be a weak link in your system security if they are not configured correctly.
Managing Mail Server Relaying and Transport between Servers
When talking about Mail Servers, one of the most persistent problems you will encounter is the number of servers that are used as Open Mail Relays by spammers. What this means is that some mail servers will happily relay mail from anyone on the Internet. I myself have witnessed dozens of mail servers improperly configured that were being used for this purpose unknowingly.
To avoid the unauthorized use of your server as an open relay, you have two options. The first is to define "Trusted Local Networks". This tells the server to go ahead and allow any computer using certain IP Addresses the ability to relay mail through your server. This works well most of the time, however if you have a firewall that forwards traffic to your mail server, you must ensure that someone outside of your network cannot relay mail using your server.
The second way to avoid the open mail relay problem is simply the option of requiring anyone relaying mail through your server to provide a username and password. This option has been overlooked in the past, but more and more ISPs are starting to go this route to fight the increase of SPAM. To do this with Suse Linux Enterprise Server, simply check the box "Require SASL Authentication". You can also setup encryption options when sending mail by enabling TLS with the Mail Server.
To configure how the mail server will talk with other mail servers, the Yast Mail Server module provides the "Mail Transport Configuration page". This page is mostly useful when you have multiple mail servers on your network that need to exchange data.
|
Purchase "Deploying Suse Linux Enterprise Server" at Lulu.com |
