A handy guide on how to select between Centralized Mail Server and Distributed Mail Server

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A distributed organization can setup its messaging infrastructure in a consolidated setup or a distributed setup. The decision between consolidation versus distribution depends on a lot of factors. However the main consideration will be the network and administrative infrastructure available.

This article details the prerequisites, advantages and disadvantages of each setup to help you decide on which architecture would suit your organization the best. The possible options are:

  1. Consolidated setups in which all mail servers are hosted at the corporate data center at one location.
  2. A distributed architecture in which every branch has its own mail server that talks to the central mail server at the corporate data center.
  3. A mixed architecture in which branch servers are installed only in those locations which do not have sufficient connectivity to the data center or the mailing requirements at this branch are special.

Pre-requisites for when to go for a consolidated setup

The following conditions are conducive to having a centralized mail server setup.

  1. Presence of a corporate data center with 24/7 administrations.
  2. Availability of adequate computing power and storage in the data center.
  3. High speed Internet connection with suitable redundancy.
  4. Sufficient bandwidth on the WAN connections to the remote branches. The bandwidth on each WAN link required will depend on all the applications running on the same and on the mail traffic and mail protocols used.
  5. A large number of branches geographically distributed with the average number of users at each branch not enough to warrant the setting up of a remote mail server.
  6. Lack of administrative resources with sufficient knowledge to manage remote mail servers.


  1. The server topology is simplified.
  2. The Mithi Connect Server servers can be administered centrally and thus reduce administrative costs.
  3. Mail Servers and other hardware devices are used optimally.
  4. A centralized data center can increase scalability and availability.
  5. With a fewer target servers; there are fewer security issues.
  6. Easier to manage mail archiving and other compliance related issues as all mail pass through the central servers.
  7. Easier to keep the mailing system up-to-date as it is easier to upgrade and patch central servers.


  1. As the end users will access their mailboxes on the central server via the network, the user experience will directly depend on the speed and availability of a connection between the branch and the data center.
  2. The network traffic between branches and the data center will increase. The traffic will be more when users access their mailboxes using the web mail client or a desktop email client. In case of access using a desktop email client, the traffic load will be more in case the client makes an IMAP connection to the server, as opposed to a POP connection.
  3. When moving from a distributed setup to a consolidated setup, the network traffic will increase substantially due the traffic generated by moving mail boxes from the branch servers to the central servers
  4. WAN bandwidth is utilized to transfer mail from one user to another even in the same branch.

Pre-requisites for when to go for a distributed setup

The following conditions are conducive to having a distributed mail server setup.

  1. A small number of branches with enough number of mail users at each branch to warrant a local mail server.
  2. Adequate administrative resources at the branches.
  3. Insufficient bandwidth capacity between the data center and branches.
  4. Messaging requirements at a particular branch are high.


  1. De-centralized administration.
  2. Low bandwidth usage on the corporate WAN.
  3. Faster mail deliveries for messages between users in the same branch.


  1. Higher administrative resources required at the branches.
  2. More security issues as the number of servers is more.
  3. Slower updates and upgrades to the mailing system.
  4. Backup and mail archiving to be done at individual branches.

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