Email server configuration scenarios

Hi friends, I am back here to discuss about a few common email server configuration scenarios before going further into the configuration part of hMailServer. I believe you would have like my previous article about Install hMailServer using MySQL as database engine a few days back. Any email server having powerful security features (like hMailServer) along with email distribution capability can be configured in a few scenarios as discussed below. As we all know the MX Record plays a vital role in email delivery system which instructs sending email server or intermediate email server where to deliver email messages destined to a domain (say

Scenario 1 : Externally Hosted Email Services

This is a very common scenario and generally seen everywhere. Here you don’t have to have email server administration capabilities because email server’s maintenance/backup/troubleshooting everything is handled by the hosting service provider. To access emails use either Web mail client or Email client, in both cases every email user must have internet access in order to send external as well as internal emails. The roaming users connect to email server using internet directly.

Scenario 1 : Externally Hosted Email Services

Scenario 2 : In house Hosted Email Services

In house live email servers are found in large corporate companies, educational organizations etc. who have IT infrastructure and administrative capabilities. The figure below assumes that you have either internal DNS server or third-party DNS services for your domain. Here all the local email users within your premises are accessing their emails over the LAN and they don’t need internet to have email facility. The roaming users will connect to the in-house email server using internet. 

Scenario 2 : In house Hosted Email Services

Scenario 3 : Primary in-house email server with external secondary email server

This is the combination of first two scenarios we discussed above. Scenario 1 has the following draw backs:

  1. All local email user’s (sitting within the premises) needs internet connectivity to external email server.
  2. When local user sends an email (say 10MB) to 5 users sitting beside her, the email goes to external email server (uploaded 10MB) and gets stored in each recipient’s mailbox (web space use 10MB x 5 recipients = 50 MB). When the recipients downloads email (downloaded 10MB x 5 recipient = 50MB). So even if all the users are within the premises on a high-speed LAN, internet 60MB of bandwidth (Uploaded 10MB + Downloaded 50MB = 60MB) is used at the same time 50MB web server space was utilized.
Scenario 2 has the following draw backs:
  1. Administrative over heads
  2. High Bandwidth internet connectivity required
  3. Dedicated hardware cost
  4. Incoming emails from internet are lost while the in-house email server is offline (either due to server issues or internet connectivity issues).
To overcome the all draw backs of scenario 1 and some of scenario 2, we can setup email infrastructure as shown in below figure. Here primary email server is hosted in-house while the secondary email server is hosted by external email service provider. This setup removes all the drawbacks of scenario 1. However it overcome only one drawback of scenario 2 as below:
  1. When the primary email server is online all emails from internet are delivered to in-house primary email server.
  2. When the primary email server is offline all emails from internet are delivered to externally hosted secondary email server where it will be queued (if external email supports) or can be stored in a catch-all or individual email account. If emails are queued in secondary email server (confirm with secondary email service provider) while primary is down, the secondary email server will try to connect the primary email server at regular interval and as soon as primary email server comes online secondary email server will deliver it to the primary email server.
  3. When primary email server comes online it will fetch all emails from catch-all or individual email account from the secondary email server.
This is the idle solution for the companies/organizations which have capability to tackle with drawbacks 1, 2 and 3 associated with scenario 2. 

Scenario 3 : Primary in house email server with external secondary email server

Scenario 4 : Email distribution server

Even scenario 3 doesn’t remove all the draw backs of scenario 2, like,

  1. Administrative over heads
  2. High Bandwidth internet connectivity required
  3. Dedicated hardware cost
However for small to medium companies who want to setup an in-house email server at the same time avoid draw backs associated with scenario 1, 2 and 3 we can implement an internal email distribution server which fetches externals emails from the email server (externally hosted) and distributes to the local users. When local users send emails to local users it is delivered locally with the email distribution server, only remote emails are sent using internet. Companies who have tens or hundreds of local email users can use setup as shown in below figure.

Scenario 4 : Email distribution server

hMailServer supports all the above discussed scenarios. In the upcoming articles we will discuss on how to setup hMailServer in each of above scenario. Keep visiting, you can subscribe to the newsletter as well.

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9 thoughts on “Email server configuration scenarios

  1. can cPanel be set with a quota for multiple mailboxes. eg 10 mailboxes = 1 gb accumulative not 10 x 100mb?

  2. I like the fact that this is easy to use and configure. Was up and
    running, receiving email within minutes Thanks to Spammers, I didn’t
    have to wait long to confirm that the smtp worked OK 🙂 Plenty of tools!
    Hooks to spamassassin and clam-win/av.

    1. spammers are very hardworking people. they keep running port scanning your IP address and as soon as they found any open ports and if SMTP (25) port is found open, they will first try to send emails without authentication and if open relay found, you are gifted with thousands of emails in queue of your email server. that’s why you should never leave open relay and also maintain strong password policy for users.

    1. thanks! Kunal, You can also subscribe to newsletter feed so that whenever I will post a new article you will get it in your mailbox.

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