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SMTP Address Rewrite, Part I

Updated: 3 days ago

In this series we talk about SMTP (Simple Mail Transfer Protocol) address rewrite solutions. They are commonly deployed in scenarios where organisations undergo changes in their email infrastructure, such as migration between email platforms or coexistence of different email environments. For example, at the time of writing, Microsoft does not allow the same domain name to be registered in two tenants. Therefore, SMTP address rewrite provides seamless communication between systems that may have different email address formats or domains.

Here are some common scenarios where SMTP address rewrite solution is coming as a handy feature or an answer to business requirements:

  • Complex email architecture. The organisation operates on-premises messaging environments and cloud-based Microsoft 365 services simultaneously or has multiple M365 tenants.

  • Consolidation as a Result of a Merger. This could lead to the consolidation of multiple cloud tenants, or on-premises environments.

  • Multi-Brand Strategy. A company might have a portfolio of products/services with different brands or names, all owned and managed by the same organisation. Additionally, the company wants to use one single SMTP domain name when communicating with the outside world.

  • Domain Name Change. An organisation undergoes a rebranding or changes its primary domain name.

In all these scenarios, the SMTP address rewrite solution acts as intermediary intercepting and modifying email addresses as they traverse different email environments, ensuring seamless and transparent user experience even during periods of change or coexistence. Proper planning, testing, and communication are essential when implementing SMTP address rewrite solutions to guarantee smooth transition and to minimise any potential disruptions in email communication.

Let's visualise the incoming and outgoing mail flow with SMTP address rewrite configured by exploring the two most common scenarios:

Email consolidation. As stated above, during mergers the goal is to consolidate multiple email systems (on-premises or cloud) into one. This process could take several months and SMTP address rewrite is ideal for achieving seamless email communication. It can be used temporarily until the consolidation is complete.

SMTP rewrite solution based on Microsoft Exchange Edge.
SMTP Address Rewrite During Consolidation of Email Systems

Multi-Brand Strategy. Another common scenario which creates challenges for the mail solution. From technical perspective this can be seen as an email consolidation which is never finished and the different mail systems are in coexistence state permanently. It is required that the global address lists between all mail systems are in sync.

Cloud-based SMTP rewrite service used to apply a multi-brand strategy
Permanent SMTP Address Rewrite for a Multi-Brand Company

In the next article from the series we are going to dig deeper by exploring one specific project our team delivered for a client.

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