Apache James

Apache James (Java Apache Mail Enterprise Server) is a modular and expandable email server running on JVM. IMAP supports SMTP, JMAP, and POP3 protocols; it also offers a distributed server version that uses technologies such as Cassandra, S3, OpenSearch, and RabbitMQ. Thanks to its Inversion of Control-based structure and James Mailet Container component, email processing, filtering and routing rules can be customized.