whatportis.com
suggest an edit →

Port 4069Minger 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..

inEmailNetwork Services
transport
udp

single transport

in transit
cleartext

payload readable on path

assignment
official

registered with iana

risk
4/10

caution

lookups
8,529

rank 590 of 993 · top 59%

Technical Details

what runs on :4069

Minger (Mail Identifier Gathering for Email Rejection) is a protocol primarily used for verifying email addresses across different servers within the same organization or federation. Instead of relying on a full SMTP connection to perform user lookup, Minger provides a method to query the existence and status of an email recipient. This reduces overhead, cuts down on unnecessary SMTP traffic, and allows quicker decision-making by mail servers.

Typically, Minger operates over UDP port 4069 to provide fast, low-latency queries. A client server sends a UDP packet containing the email address in question to the Minger server, which responds with a simple message indicating if the address exists or not. Since the responses are lightweight, this process enhances performance when compared to conventional methods like SMTP VRFY.

Minger was developed primarily by Alt-N Technologies for its MDaemon Email Server ecosystem, but the protocol's simplicity allows it to be adopted by other compatible mail transfer agents. Despite its narrow adoption, it serves a specific niche for rapid, efficient intra-organization email validation without exposing full user details or requiring encrypted connections.

Security Information

exposure of :4069

risk score

4/ 10caution

worth attention. how exposed you are depends on configuration — don't leave it reachable from the internet without a reason.

email averages 3.9 across 42 ports — this one sits 0.1 above.

in transit

cleartext

credentials and payloads are readable by anyone on path

assignment

official

registered with iana for this service — scanners fingerprint it by number

reachable over

udp

udp is connectionless — source addresses are trivially spoofed and it is a reflection favourite

security overview

Common vulnerabilities associated with Minger include:

  • Information Disclosure: Because Minger responds to verification queries without authentication, it can be used to enumerate valid email addresses on a server, facilitating targeted phishing attacks or spam campaigns.
  • UDP Amplification Attacks: Since it relies on UDP, it may be susceptible to amplification in DDoS attacks if improperly rate-limited.
  • Lack of Encryption: Data transmitted is unencrypted, enabling attackers on the network to intercept queries and responses.

Mitigations include:

  • Access Controls: Restrict which IP addresses or networks can issue Minger queries to trusted internal or federated servers only.
  • Rate Limiting and Logging: Implement abuse detection and throttling to prevent enumeration or amplification abuses.
  • Network Segmentation: Use network firewall rules to limit exposure of port 4069.
  • Migration to Encrypted Channels: If feasible, encapsulate Minger queries within VPN or other encrypted tunnels to reduce interception risks.

Related Ports

all 42 in email →

the 8 most looked-up other ports in email — 42 ports carry that label.

portservicerisk
:143IMAPcaution
:995POP3Scaution
:109POP2caution
:2096cPanel SSL Webmailsafe
:110POP3caution
:993IMAPScaution
:1352Lotus Notes RPCcaution
:24Private Mailcaution

risk mix of the 8 listed

  • safe13%
  • caution88%

3 of 8 encrypted