LDAP and Sendmail offer sys admins considerable advantages for dynamic mail routing and centralized alias management. A common requirement, as an organization grows, is to support geographically dispersed mailservers. While this can be achieved by using subdomaining (i.e., email@example.com, firstname.lastname@example.org), it is generally preferable to route the mail dynamically from a single address (email@example.com). I'll explore how this can be accomplished using Sendmail in conjunction with OpenLDAP.
A similar problem faced by administrators is dealing with growing and disparate "/etc/aliases" databases. These files are often maintained individually on a per system basis and, in the case of load balanced mail servers, need to be kept in sync manually. An alternative to individually maintaining each file is to migrate the alias data into an LDAP directory. I'll examine how to configure Sendmail to use OpenLDAP to accomplish this.
Finally, LDAP APIs exist for practically every common development platform. This gives the sys admin the ability to implement Web front-ends, command-line scripts, etc. to manage routing entries and aliases. It also provides developers an easy entry point for integrating application functionality with the organization's mail systems in a standard way.
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