Do these 3 things before closing this tab:
1Repair Windows errors before they cause bigger problems2Fix the driver behind crashes, sound loss and screen glitches3Clear out junk files and repair common Windows errorsExpose only the Zimbra services your organization actually uses. For inbound Internet email, the MTA must be reachable on TCP port 25. Users may also need HTTPS webmail and selected client protocols such as SMTP submission, IMAP, or POP. Keep administration and backend services private or restricted to trusted networks. Zimbra’s port inventory is a deployment-review reference—not a universal firewall allowlist—and is marked as a work in progress.
Start with the services users and other mail systems need
Build the perimeter around your deployment’s actual mail flow and enabled features. Zimbra’s port reference separates services typically available to clients from those used internally; its external-access list does not mean every listed port should accept connections from the public Internet. Zimbra’s guidance is to be restrictive. See the Zimbra port reference.
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- Inbound email: Internet mail servers need to reach the MTA on TCP 25. Zimbra identifies this as necessary for inbound mail flow in its incoming mail flow troubleshooting guidance.
- Webmail: Publish HTTPS on TCP 443 if users access Zimbra in a browser. HTTP on TCP 80 appears in the inventory, but whether it is needed depends on your configuration; do not assume it must be publicly available.
- Mail clients: Enable only the protocols your users rely on. The inventory includes POP3 on 110, IMAP on 143, SMTPS on 465, submission on 587, IMAPS on 993, and POP3S on 995. Prefer encrypted access paths where supported and configured.
- Optional features: XMPP on 5222/5223, certificate connection on 3443, and proxy administration on 9071 are listed, but should be exposed only when the feature and access pattern are needed. Administration access should be restricted, not treated as ordinary client traffic.
For HTTPS-only proxy and mailstore modes, and TLS between proxy and upstream services, consult the applicable Zimbra configuration guidance. Proxy and upstream settings must be consistent for the chosen mode.
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Restrict management access
Do not expose the administration UI on TCP 7071 or proxy administration on 9071 to the general Internet. Zimbra’s security operations guidance advises avoiding public administration interfaces and using VPN access; it also describes SSH tunneling as an option. Restrict SSH and administrative access to a VPN or known source IP addresses.
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Control internal service connections
The port reference lists LDAP on 389/636, LMTP on 7025, milter on 7026, conversion on 7047, mailbox administration on 7071, and lookup/authentication on 7072 among internal-access examples. These support system or node communication; they are not a public-client checklist. Permit them only where required by the deployment, such as between trusted nodes or local services. Exact rules depend on topology.
Zimbra describes MTA and Nginx as Internet-facing services that manage and protect client connections to internal services. A common design principle follows: public traffic should terminate at the intended edge services, while backend and inter-node services remain private. The right implementation depends on where your proxy, MTA, and mailbox services run.
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Review the firewall in a deployment-specific order
- Confirm inbound mail routing. Check that public MX records resolve as intended and that the firewall forwards TCP 25 to the designated MTA. A mismatch can prevent inbound delivery even when other client services work.
- List enabled user services. Identify whether users need webmail, IMAP, POP, SMTP submission, XMPP, or another optional service. Allow only the required protocols and ports from the relevant networks.
- Identify the public edge. Record whether Internet connections reach a proxy/MTA tier or mailbox nodes directly. Confirm that exposed services match that design and that backend connections are limited to required internal peers.
- Restrict management paths. Limit SSH and administration interfaces to VPN users or approved source addresses. Do not make a management port public simply because it appears in the port inventory.
- Review proxy allowlists. Zimbra’s 8.8.15 P25 release guidance warns that unsafe or wildcard
zimbraProxyAllowedDomainsentries resolving to internal addresses could provide access to services on ports not otherwise intended to be public. Review the 8.8.15 P25 release guidance in the context of your installed release, and use specific trusted hosts rather than broad wildcards. - Patch and monitor. Follow current security-update guidance for your supported Zimbra release and operating system. Zimbra’s security operations page also discusses host firewalls and brute-force mitigation; old examples should not substitute for instructions applicable to your installed version.
Why version and topology change the answer
The port reference is explicitly a work in progress, and Zimbra’s documentation page lists current Daffodil v10 documentation alongside upgrade paths for older deployments. Use the documentation for your installed release rather than applying a port list as if it covered every version and architecture. See Zimbra’s documentation and upgrade paths.
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Before writing exact firewall rules, establish the Zimbra release and patch level, enabled user protocols, single- or multi-node layout, and proxy placement. Two deployments may use different public ports because they provide different services or route traffic through different tiers; the available port reference does not provide a complete current matrix for every supported architecture.
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