Email Ports

IMAP

Internet Message Access Protocol (IMAP) enables email clients to access, manage, and synchronize email messages stored on a remote mail server. Unlike older protocols like POP3, IMAP allows users to view their mailbox contents from multiple devices while keeping messages on the server, maintaining consistent state across platforms. IMAP supports functions such as folder management, message searching, selective download, and flagging, providing a comprehensive solution for modern email management as defined in RFC 3501.

POP3S

POP3S (Post Office Protocol Version 3 Secure) provides encrypted email retrieval for clients accessing their mailbox from mail servers, ensuring user authentication and message data remain protected during transit. It is essentially the secure version of POP3, using TLS/SSL to add a layer of encryption to prevent eavesdropping or tampering. POP3S is widely supported in mail clients and offers a simple, dependable method to securely access email stored on remote servers.

POP2

The Post Office Protocol version 2 (POP2) is an early email retrieval protocol designed to facilitate the transfer of email messages from a remote mail server to a local client. Developed in the 1980s, POP2 supports basic operations for listing, retrieving, and deleting messages stored on the server. Despite its historical significance, POP2 has largely been replaced by the more advanced and secure POP3 protocol due to evolving email requirements and the need for enhanced security.

cPanel SSL Webmail

Port 2096 is commonly used by cPanel's webmail service over an encrypted SSL/TLS connection. It enables users to securely access their email accounts via a web-based interface, providing convenient email management for domains hosted on servers utilizing cPanel. The SSL encryption ensures data privacy during transmission, protecting sensitive email content from interception by unauthorized parties.

POP3

Post Office Protocol version 3 (POP3) is a widely used email retrieval protocol designed to allow email clients to download messages from a mail server for local storage and offline access. Operating on TCP port 110, POP3 facilitates the transfer of emails from the server to the client, emphasizing simplicity and minimal server-side resource use.

IMAPS

IMAPS (Internet Message Access Protocol Secure) is the encrypted version of IMAP that enables secure retrieval of email messages from a mail server over SSL/TLS. It protects the confidentiality and integrity of email content during transit, ensuring user credentials and emails remain private against eavesdropping and tampering.

Lotus Notes RPC

Port 1352 is primarily used for IBM Lotus Notes and Domino servers to communicate using a proprietary Remote Procedure Call (RPC) protocol. This protocol facilitates messaging, database, and directory services within the IBM collaboration suite, ensuring clients and servers exchange commands and data efficiently across networks.

Private Mail

Port 24 is traditionally assigned for private mail systems, serving as a dedicated communication channel distinct from standard email protocols. This port is seldom used in modern network infrastructures but may still be encountered in legacy or proprietary messaging environments. Its primary function involves facilitating the transfer and exchange of email-like messages within closed or controlled networks.

Zimbra LMTP

Port 7025 is primarily used by Zimbra Collaboration Suite's LMTP (Local Mail Transfer Protocol) service for internal mail delivery within the Zimbra server environment. It facilitates the transfer of email messages between the mailbox server and other components handling incoming emails, ensuring reliable and efficient local message distribution.

cPanel Webmail

Port 2095 is primarily used by cPanel hosting control panel installations for providing unsecured webmail access. This allows users to access their email through a web interface when connecting to their hosting provider's cPanel-managed services. Despite its convenience, this port transmits data in plaintext, making encrypted alternatives recommended for secure communication.

VPOP3 Status

VPOP3 Mail Server is a Windows-based POP3/SMTP email server that provides businesses with internal and external email handling capabilities. Port 5109 is used for status and management communication between client tools, monitoring systems, and the server itself. It facilitates administrative tasks such as checking the health of the mail server, reviewing messages in queue, and managing configuration remotely.

SMTP

SMTP (Simple Mail Transfer Protocol) is one of the core protocols used for sending emails across the Internet. It facilitates the reliable transfer of outgoing mail between email servers and from email clients to servers, enabling seamless global communication. Operating primarily over TCP port 25, SMTP ensures that messages are relayed efficiently, serving as the foundation of modern Internet email infrastructure.

SMTP over SSL

Port 465 is commonly used for secure SMTP communication, encapsulating email transmission within SSL encryption. This port facilitates encrypted email delivery between clients and mail servers, enhancing privacy compared to traditional plain-text SMTP connections. Although it was initially designated as a secure SMTP port, its status has shifted over time, but it remains widely supported for legacy encrypted email connections.

ACAP

**ACAP (Application Configuration Access Protocol)** is a protocol designed primarily for the storage, retrieval, and management of user configuration data and preferences across multiple devices or applications. It facilitates centralized access to user-related data such as bookmarks, contact lists, and email preferences, making user profiles portable and synchronized across distributed clients.

SMTP Submission

Port 587 is primarily used for the submission of email messages over the Simple Mail Transfer Protocol (SMTP). It is designated for client-to-mail server communication, allowing authenticated users to send outgoing emails securely, typically requiring authentication and optional encryption. This port replaces legacy port 25 for authenticated message submission to improve security and adherence to email standards.

Exchange Routing

Port 691 is used by Microsoft Exchange Server for routing email messages within and between Exchange servers in an organization. It plays a vital role in facilitating message transport and ensuring efficient communication across the messaging infrastructure.

Mail Transfer Protocol

Mail Transfer Protocol (MTP) was an early protocol designed to transfer electronic mail reliably across computer networks. It predated SMTP and provided basic functionalities to send, relay, and receive messages, but due to limitations and evolving requirements, it was largely deprecated in favor of more robust standards like SMTP.

ODMR

On-Demand Mail Relay (ODMR) facilitates mail delivery by allowing remote servers to retrieve queued email messages as needed, rather than relying solely on traditional push-based SMTP delivery. This enables efficient mail forwarding in scenarios where recipient servers have intermittent connectivity or are located behind firewalls, enhancing email flexibility for ISPs and mobile users.

Internet Message Mapping Protocol (IMMP)

The Internet Message Mapping Protocol (IMMP) is designed to facilitate message synchronization and mapping between messaging systems, aiding interoperability across disparate email services and platforms. Supporting both TCP and UDP transports, IMMP aligns with multi-environment messaging needs and provides the foundation for translating message metadata effectively. Its use case centers on connecting heterogeneous communication systems without standardized protocols for efficient message delivery.

SonicWALL Antispam

Port 2599 is utilized by SonicWALL's Antispam service for communication between the Remote Analyzer (RA) and the Control Center (CC). This dedicated connection enables real-time transfer of spam analysis data, updates, and coordination commands, facilitating effective centralized spam filtering across distributed email environments.

XNS Mail

Xerox Network Systems (XNS) Mail is a legacy protocol designed by Xerox to facilitate electronic messaging within its proprietary network architecture. Developed in the late 1970s and early 1980s, XNS Mail was foundational for early email communication in Xerox's internetworking environment prior to widespread TCP/IP adoption.

Zimbra SMTP Amavis Integration

Port 10025 is commonly used internally within Zimbra Collaboration Suite to facilitate the relay of email messages from the Amavis content filter back into the Postfix Mail Transfer Agent (MTA). This port enables scanning and filtering of emails for malware, spam, or policy compliance before final delivery, serving as a secure and structured point of reinjection after content analysis.

Zimbra SMTP to Amavis

This port is commonly used within Zimbra Collaboration Suite for internal communication between the mail transfer agent (Postfix) and Amavis, an open-source content filter. It facilitates email scanning, virus filtering, and spam detection before mail delivery, ensuring cleaner email flows within an organization’s email infrastructure.

IMAP v3

IMAP version 3 (Internet Message Access Protocol) enables users to access and manage their email messages stored on a mail server in real time. It allows multi-device email synchronization, giving users flexibility to organize mail folders remotely and retrieve messages without downloading them permanently. This protocol version builds upon earlier iterations for improved client-server interaction, enhancing email management efficiency for both personal and organizational use.

Minger Email Verification

Minger is a lightweight protocol used primarily with email servers to verify the existence and validity of email addresses without initiating full SMTP transactions. Designed originally for integration with the MDaemon Email Server, it helps email systems quickly validate addresses to minimize bounce rates and improve efficiency in mail routing.

Zimbra Conversion Server

Port 7047 is used primarily by the Zimbra Collaboration Suite's conversion server component, which facilitates document and attachment content conversion within the Zimbra environment. It enables the transformation of various file formats to ensure browser and client compatibility, supporting streamlined mail and collaboration workflows.

Remote Mail Checking

The Remote Mail Checking Protocol (RMCP) is an early protocol designed to facilitate remote access to email servers for users to verify mail status without downloading full email content. It enables lightweight communication to determine if new messages are present, providing basic functions similar to what modern POP3 would later formalize. Its use has diminished over time due to advances in email retrieval technologies and secure protocols.

KPOP - Kerberos POP

KPOP, or Kerberos Post Office Protocol, is a secure adaptation of the Post Office Protocol (POP) that leverages Kerberos authentication. It was designed to provide stronger security measures for email retrieval by integrating Kerberos' trusted ticket-based authentication system, thereby reducing risks associated with password-based methods.

VPOP3 Webmail

VPOP3 Mail Server Webmail provides a web-based interface for users to access their email hosted on VPOP3 servers. It enables convenient email management via standard web browsers, offering features such as sending, receiving, and organizing emails without requiring dedicated email client software.

Novell GroupWise

Port 1677 is primarily used by Novell GroupWise for client/server communication, facilitating email messaging, calendaring, and other collaboration features. It supports both TCP and UDP protocols to maintain efficient connectivity between GroupWise clients and servers in a business environment.

UUCP Path

The UUCP Path Service (port 117) facilitates path services for the Unix-to-Unix Copy Protocol (UUCP), enabling exchange of email routing and network addressing information among interconnected Unix systems. Historically vital for email and file transfers before the rise of TCP/IP and the Internet, this service plays a role in maintaining communication paths within UUCP networks.

comsat & biff

The Comsat service, working alongside the `biff` notification utility, provides users with real-time notifications of new email arrivals on UNIX systems. It leverages UDP to listen for incoming mail notifications and alerts logged-in users when new messages are received, historically enabling immediate awareness of incoming communications.

Zimbra MySQL Mailbox

Port 7306 is primarily used within Zimbra Collaboration Suite to facilitate database communication between mailbox servers and their associated MySQL backend. As an internal service port, it enables critical storage and retrieval operations essential for email and collaboration functionalities. The port typically listens for connections from Zimbra components, rather than external clients.

Zimbra MySQL Logger

Port 7307 is utilized by Zimbra Collaboration Suite as a MySQL logger service, supporting backend operations like email indexing, logging, and internal database management. It facilitates communication between Zimbra components, maintaining system health and operational data tracking.

DMSP

Distributed Mail Service Protocol (DMSP) was designed as an email transport protocol facilitating distributed mail delivery and management across multiple servers. Operating on port 158, DMSP supports both TCP and UDP for flexible communication paths. While largely supplanted by more modern and secure protocols, it historically aimed to optimize email routing in decentralized architectures.

SpamAssassin spamd

SpamAssassin's spamd daemon listens on port 783 to perform content-based email filtering, identifying spam through a vast array of heuristic and signature-based tests. Designed to work alongside mail transfer agents, spamd enables rapid analysis of inbound mail streams, efficiently tagging or rejecting unwanted messages. It is a popular tool integrated into many email security solutions to reduce spam volume and protect users from unsolicited messages and common email threats.

SMTPS

Port 465 was initially used for the Secure SMTP (SMTPS) protocol, providing encrypted email transmission via SSL. Despite its early deprecation in favor of STARTTLS on port 587, it has seen a resurgence in use for secured email submissions. This port helps facilitate confidential communication between email clients and servers, ensuring message privacy over potentially insecure networks.

Binkp Fidonet Mail

**Binkp** is a protocol designed to facilitate the exchange of Fidonet mail packets over TCP/IP networks, utilizing port 24554. Originally developed to modernize the transfer of echomail and netmail across Fidonet nodes, Binkp allows traditional store-and-forward bulletin board systems to communicate reliably over the Internet, rather than legacy dial-up methods.

FirstClass Protocol

FirstClass Protocol is a communication platform suite primarily used in educational institutions and businesses for email, collaboration, and messaging. It runs on a proprietary protocol that facilitates client-server interactions for groupware functionalities. Port 510 is traditionally utilized during server communication within FirstClass systems to enable seamless integration of messaging, conferencing, directory services, and administrative tasks.

Quick Mail Transfer Protocol

The Quick Mail Transfer Protocol (QMTP) is a rapid mail transfer system designed primarily to facilitate quick and efficient routing of electronic mail messages over a network. Unlike traditional mail protocols that focus on extensive feature sets, QMTP prioritizes fast data transmission between mail hosts with minimal overhead, catering to circumstances where speed and simplicity are essential. Though not widely adopted compared to SMTP, it serves niche applications where throughput and performance are critical factors.

Citadel Groupware

Port 504 is primarily used by Citadel groupware, a collaborative client-server platform offering email, calendar, contacts, bulletin boards, and more. This port facilitates dedicated Citadel protocol communications between specialized clients and the Citadel server, enabling multiservice access within the unified groupware environment. Both TCP and UDP are supported for flexible and reliable data transfer, underpinning internal messaging, directory access, and real-time collaboration functions.

SMTP Alternate

Port 2525 is widely used as an alternative SMTP (Simple Mail Transfer Protocol) port for email message submission, particularly as a workaround when ISP restrictions or firewall policies block the default SMTP port 25. While unofficial, it has become popular among email service providers for facilitating reliable outbound email delivery.