Apache James, the modular Java mail server, running as a single node SMTP and IMAP appliance with its mailbox store, search index and mail queue all built in.
Apache James (Java Apache Mail Enterprise Server) is a long established open source mail server from the Apache Software Foundation, built as a modular platform rather than a fixed product. It provides a full SMTP transfer agent for sending and receiving, IMAP mailbox access with STARTTLS and implicit TLS, Sieve filtering, and a programmable mailet container that lets you route, rewrite, filter and act on mail with ordinary Java logic instead of a bespoke configuration language.
This is the single node distribution, so the mailbox store, the full text search index and the mail queue all run inside the one process. There is no database server to operate, no search cluster and no message broker, which makes it a genuinely self contained mail server for a domain, a team or an application that needs to receive and store mail on infrastructure it controls.
cloudimg ships Apache James fully installed and configured as an appliance, so a working mail server is answering minutes after launch with nothing to build or wire together. Nothing ships with a known credential: the image contains no mailbox, no TLS private key and none of the upstream default passwords, and on the first boot of every instance a one shot service mints a unique TLS keypair named for that instance, unique datastore credentials and a unique postmaster password written to a file only the root user can read. The upstream sample configuration that would relay mail for anything on the local machine without authentication is removed, so authentication is required for every relay, and each build proves end to end that a real message is submitted, delivered and retrieved, that an open relay attempt is refused, and that inbound mail is still accepted. The administrative API is bound to the loopback interface so your own SSH key is the front door. Every deployment is paired with a step by step deploy guide that covers the platform's outbound mail restrictions honestly, backed by 24/7 cloudimg support.