Design goals

Complete solution The mail system is able to handle both mail transport and storage in a single server application. Apache James works alone without the need for any other server or solution.

Customisable solution Apache James behaviour can be easily extended by the means of several plugin extensions, for instance mailets, Mailbox listeners, SMTP hooks, SMTP commands, or WebAdmin routes, for instance.

Horizontally scalable email server Apache James uses resource abstraction (see below) to provide and assemble the components of a Distributed Email server based on modern, scalable NoSQL solutions: Cassandra, objectstorage, OpenSearch, RabbitMQ/Pulsar.

Protocol abstraction Unlike other mail engines, protocols are seen only like "communication languages" ruling communications between clients and the server. Apache James is not be tied to any particular protocol but follow an abstracted server design (like JavaMail did on the client side)

Mailet support Apache James supports the Apache Mailet API. A Mailet is a discrete piece of mail-processing logic which is incorporated into a Mailet-compliant mail-server's processing. This easy-to-write, easy-to-use pattern allows developers to build powerful customized mail systems. Examples of the services a Mailet might provide include: a mail-to-fax or mail-to-phone transformer, a filter, a language translator, a mailing list manager, etc. Several Mailets are included in the James distribution (see server documentation).

Resource abstraction Like protocols, resources are abstracted and, accessed through defined interfaces (like JPA for mailbox or user accounts in RDBMS's). The server is highly modular and reuse solutions from other projects. Thanks to the modularity of the servers, you can use James as a toolkit to assemble your own mail server. Select which components of Apache James you want to use, in which combinaison, and even write your owns.

Anything else you may want if you help us write it :-)

Standard compliance

It is the existence of published "open" standards which allows independent teams to develop interoperable software.
James attempts to support a number of these standards most of which are IETF RFC's and in the areas covered by these standards the published standard is our requirements document.
This sometimes leads to confusion where behaviour is not the subject of a relevant standard, or conflict where common (de-facto) behaviour is actually at odds with a supported standard.
We believe that it is our responsibility to adhere to the published standard. If we allow our implementation to deviate it means that we are tacitly encouraging the situation whereby interoperability is no longer guaranteed by standards compliance alone, but also requires access to undocumented and possibly even commercially licenced technology. There is no easy route for a newcomer to acquire these secrets, and interoperability becomes something only available to the elite.

The James policy for issues of non-compliance tries to tread the fine line between a pragmatic acceptance of other people's misinterpretation of the RFC's and an evangelical defence of open standards as the key to freedom of inter-operation.

In practice this policy is that certain well argued of cases of non-compliance which can be *safely* worked around, will be tolerated by James.

In cases (like jira issue JAMES-344 ) where variance from a published standard is required it is desirable that this functionality is disabled in James by default, it must be prominently and clearly documented that this causes James to violate the relevant standard, and should be enabled by explicit configuration, making its use a conscious decision of the user rather than an decision taken by the James team.

In cases where the required behaviour is not within the scope of any standard which James claims to support (such as behaviour which is a de-facto standard or an internet draft RFC but not yet subject of a standards track RFC) it is acceptable to implement the behaviour so long as it is adequately documented (for instance by reference to an internet draft or other public document) and users can be clear about what to expect from James.