Setting Mail Servers on a Unix Environment - Report Example

SETTING MAIL SERVERS ON A UNIX ENVIRONMENT. UNIX is an operating system that was developed by Ken Thompson and Dennis Ritchie in bell labs at around 1969. It was originally coded in the C programming language and has been maintaining the same programming language. Since its inception it has evolved to become one of the major free operating system under different versions partly because it was not owned by any other Information Technology organization and also it has been coded by a standard language which has been embraced by very many popular ideas. Today the UNIX trademark is owned by Open Group the organization which also has the responsibilities and rights of certifying and branding all UNIX implementations across the world. A good example of UNIX operating system is the Sun Solaris which was developed by sun Microsystems as the successor to their previous Sun OS. Solaris is widely reputed for its scalability and compatibility with x86 based workstations and servers. Most of Solaris codebase is open- source all these being courtesy of Solaris open project initiatives. In this Guide I have chosen Solaris 9 as the reference and any explanation henceforth will be under Solaris 9. This will be a step by step instruction on how you set up a mail server on a UNIX operating system. However before you are able to accomplish your goals. A couple of products both software and hardware will be needed in order for you system to function effectively. In this regard I have chosen Sun Solaris because it has inbuilt programs bundled with it but with the hardware it has to be specially dedicated. However the author of this guide assumes that the readers are well versed with Suns Solaris operating system and also familiar with UNIX environment. Software’s -Sendmail Hardware requirements for a mail server. 1. Mail host: It handles all the mails that are difficult to resolve by the clients. In most cases a mail host will be the designated main email machine in the network and also the one which all undelivered mails will be forwarded to. The system will work best if it is configured as a router on the internet, however it can be set up in various ways but these are the simplest and widely used. 2. Mail server:-It is a single file configured to contain mails from a particular user, it is configured to handle one or more mailboxes, the hardware can be on a local machine or on a remote server. It puts the mail in some sorts of queue after the client has sent the emails. Incase the recipient receives an email the “FROM” message contains the name of the mail server machine. However a good candidate for a mail server should be a system that is regularly backed up. If users on your system send large files such as audios and video clips you will need to allocate more storage space to your system for the mailboxes. Having a mail server for the mailboxes will always save you the agony of repetition but incase of a single failure most users will be inconvenienced completely. 3. Mail Clients:-These are system that are designed to access the emails from the mail server but they do not have a local directory..I.e. they do not have the /var/mail directory. 4. Mail Gateway:-If users within your domain would like to communicate outside your main domain then you need a mail gateway, It simply handles communications between networks that needs different communication protocols. You need it to receive and send emails outside the domain. It uses sendmail to send and receive mails outside the domains. This can be illustrated by the diagram below. However before an email configuration setup is preformed the following things should be taken into account. (1)You should always determine the type of email configuration that will meet your requirements, (2)choose systems that will act as the mail servers, hosts and gateways, (3)list all the clients you will be providing services for together with location of their mailboxes and don’t forget in updating aliases together with forward mail messages. Setting up a mail server. After you have completed the planning processes you will now need to do the following: The user must have an entry in the password file or in the namespace. Also, for the Emails to reach their destination, Also there must be a local home directory for the sender for checking the ~/.forward file. And this is the main reason why all home directory servers are often set up as the mail server. The mail server can route mail for many mail clients. This type of mail server must have adequate spooling space for client mailboxes. Note – In order to acess your mailboxes, the /var/mail directory should be available for remote mounting. Alternately, a service such as Post Office Protocol or Internet Message Access Protocol should be available from the server. The procedure below shows you how to set up a mail server by using the /var/mail directory. For the following task, make sure that the /etc/dfs/dfstab file shows that the /var/mail directory is exported. 1. Make sure you are the super user on the mail servers. 2. Stop sendmail. # /etc/init.d/sendmail stop 3. Check if the /var/mail directory is already available for remote access. # share If the /var/mail directory is listed, ensure that your name service has been started. If the /var/mail directory is not listed or if no list appears, continue with the appropriate substep. a. (Optional) If no list appears, start NFS services. “when you are setting up the automatic NFS services” use the /var/mail use the directory to start NFS services. b. (Optional) If the /var/mail directory is omitted, add the directory to /etc/dfs/dfstab. Add the following command line to the /etc/dfs/dfstab file. share -F nfs -o rw /var/mail 4. Avail the file system for mounting. shareall 5. Make sure that your name service has been started. a. (Optional) If you are running the NIS then this is the command ypwhich b. (Optional) If you are running NIS then this is the command command. nisls. c. (Optional) If you are running DNS then this is the command. nslookup hostname hostname Use your host name. d. (Optional) If you are running LDAP then this is the command. Ldaplist 6. Restart sendmail. # /etc/init.d/sendmail start The mail.local program automatically will creates /var/mail directory the first time a message will be delivered. You will no longer need to create individual email boxes for the email clients. How to Set Up a Mail Client 1. Make sure you are the super user. 2. Stop sendmail. # /etc/init.d/sendmail stop 3. Ensure that a /var/mail is existing on the mail client’s system. The mount point should have been created during the installation process. You can try to use ls to ensure that the file system exists. The following example shows theresponse that you receive if the file system has not been created. # ls -l /var/mail/var/mail not found 4. Ensure that no single files is in the /var/mail directory. If mail files do exist in this directory, you should move them so that they are not covered when the /var/mail directory is mounted from the server. 5. Mount the /var/mail directory from the mail server. You can mount the mail directory automatically or at boot time. a. (Optional) Mount /var/mail automatically. Add an entry such as the following to the /etc/auto_direct file./var/mail -rw,hard, actimeo=0 server:/var/mailserver Use the assigned server name. b. (Optional) Mount /var/mail at boot time. Add the following entry to the /etc/vfstab file. This entry permits the /var/mail directory on the mail server that is specified to mount the local /var/mail directory. server:/var/mail - /var/mail nfs - no rw,hard,actimeo=0 The client’s mailbox is always automatically mounted whenever the system is rebooted. If you are not rebooting the system, perform the following command to mount the client mailbox.# mountall 6. Update /etc/hosts. Edit the /etc/hosts file and add an entry for the mail server. The step is not mandatory if you are using a name service. required if you are using a name service. # cat /etc/hosts # # Internet host table # .. 7. Add an entry in any of the alias files. Note – The mail.local program automatically creates mailboxes in the/var/mail directory the first time a message is delivered. 8. Restart sendmail. # /etc/init.d/sendmail start How to Set Up a Mail Host 1. Make sure you are the super user. 2. Stop sendmail. # /etc/init.d/sendmail stop 3. Host-name configuration verification. Run the check-hostname script to verify that sendmail is identifying the qualified host name for this server.% /usr/lib/mail/sh/check-hostname hostname phoenix OK: fully qualified as phoenix.example.com 4. Update the /etc/hosts file. Choose any of your preffered procedures.. a. (Optional) If you are using NIS or NIS+, edit the /etc/hosts file on the system that is to be the new mail host. Add the word mailhost and mailhost.domain after the IP address and system name of the mail host system.IP_address mailhost mailhost.domain loghostIP_address Use the assigned IP address. mailhost Use the system name of the mail host system.domain Use the expanded domain name. The system is now designated as a mail host. The domain should be identical to the string that is given as the sub domain name in the output of the following command. % /usr/lib/sendmail -bt -d0 Read More