Benefits of Using the :Fail: Directive for EXIM Catchall on cPanel

April 24, 2023 / Web Hosting

Fail: Directive for EXIM

In this post, we will discuss how those using the EXIM mail transfer agent on a cPanel server would be better to use the :fail: directive and not :blackhole: directive for the default, catchall email address.

What are catchall addresses?

Companies need a catchall email address to ensure that no emails are lost. A catchall email address is set up to receive all emails that are sent to addresses that do not exist on the company’s email server, for instance, if a sender mistakenly gets the domain part of the email address right but types the recipient’s name wrong (e.g., jhon@ instead of john@).

This can be useful for a number of reasons, including:

If an email is sent to an address that does not exist, it will be bounced back to the sender. However, if the company has a catchall email address, the email will be delivered to the catchall address as well as being bounced back. This ensures that the email is not lost.

Spammers often send emails to addresses that do not exist. If the company has a catchall email address, it can collect information about the spam, such as the sender’s IP address and the content of the email. This information can be used to block spam and track down spammers.

If a company does not have a catchall email address, it may appear unprofessional to potential customers or partners. This is because it may seem like the company does not have a good system in place for handling email.

Domain Name

What is EXIM?

EXIM (short for Exim Message Transfer Agent) is a popular open-source mail transfer agent (MTA) software for Unix-like operating systems. It is widely used for sending and receiving email messages on servers and is often the default MTA included with many Linux distributions. It is estimated that today (2023), almost 60% of publicly reachable mail servers on the Internet currently run EXIM.

EXIM is highly configurable and has a powerful set of features that make it suitable for use in a wide range of email server setups. Some of its key features include support for multiple domains and virtual domains, flexible routing based on a wide range of criteria, extensive filtering capabilities, support for multiple authentication mechanisms, and support for multiple transport mechanisms such as SMTP, LMTP and more. EXIM is included in cPanel / WHM.

Benefits of using :fail: instead of :blackhole:

There are sound technical reasons to use the :fail: directive instead of the :blackhole: directive on a cPanel server running EXIM.

The :fail: and :blackhole: directives are both used to discard messages, but they do so in different ways. With :fail:, messages are rejected immediately, at the SMTP level. This means that the message is never accepted by the server, and no CPU or bandwidth resources are wasted on processing or storing it.

With :blackhole: the message is accepted but is then delivered to a null router, which effectively means that it is discarded. As a result, the message is processed by the server, which can take up resources. It is also stored, taking up space on the server, even if it is only for a short time.

Here are some of the specific reasons why you should use :fail: instead of :blackhole: on a cPanel server running EXIM:

  • :fail: saves bandwidth
    When you use :blackhole:, the entire message is accepted and received on the server. This wastes bandwidth as the server has to download the entire message even though it is going to be discarded. :fail:, on the other hand, rejects the message immediately, so the server never has to download it.
  • :fail: saves server resources
    As :blackhole: processes the entire message, even though it is going to be discarded, it can waste server resources, such as CPU time, memory and disk I/O. :fail:, on the other hand, does not process the message at all, so it saves server resources which can improve the performance of other server workloads.
  • :fail: complies with SMTP RFCs
    When you use :blackhole:, the server does not send a bounce message to the sender of the discarded message. This is a violation of SMTP RFCs, which require that bounce emails are sent to let the user know their message didn’t arrive where intended. :fail:, however, always sends a bounce message and so complies with SMTP RFCs.
  • :fail: can protect against spam
    Spammers are less likely to send messages to addresses that they know will be rejected immediately. As :fail: rejects messages straight away, it can help to protect your server from spam, whereas :blackhole: does not reject messages immediately, thus making it less effective.

Conclusion

After reading this article you should now understand what a catchall email address is and the importance of having one. You should also know what EXIM is and, if you use it on cPanel, why it is better to use the :fail: directive than the :blackhole: directive if you want to use fewer resources, comply with SMTP RFCs and protect your server from spam.

Looking for fast, secure and affordable cPanel Hosting? Check out our Web Hosting with cPanel page.

Author

  • Arjun Shinde

    I'm an experienced digital marketer with expertise in planning, SEO, SEM, and social media. I'm good at creating engaging content and optimising campaigns for a strong online presence.

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