Cyber Security
Proxmox Mail Gateway Deployment and Support
Filter spam, viruses and phishing emails with Proxmox Mail Gateway before they reach your mail server; get deployment, licensing and support from Synchron.
What is Proxmox Mail Gateway?
Proxmox Mail Gateway (PMG) is an open-source email security gateway that sits between your firewall and your internal mail server. All inbound and outbound email traffic passes through this layer; messages with spam, viruses, trojans or phishing content are filtered out before they reach users.
PMG works with common mail servers, above all Microsoft Exchange and Postfix. It installs as software or as a virtual appliance, is managed from a web-based interface and is distributed under the GNU AGPLv3 license. It protects an unlimited number of email domains and several internal mail servers from one point.
As of October 2026, the current release is Proxmox Mail Gateway 9.1.
Proxmox Mail Gateway with Synchron
As a Proxmox Authorized Reseller, Synchron deploys your email security layer, tunes the rules to your organization and takes over its day-to-day operation. Fine-tuning the filter to reduce false positives is as much part of our work as deploying it.
Deployment and integration
We deploy PMG in a virtual or physical environment and configure the MX records, the connection to your mail server and, where needed, a high-availability cluster.
Rule and policy design
We design organization-specific block and allow lists, attachment policies and quarantine rules that do not disrupt your business processes.
License and subscription sales
We choose the right subscription level for each PMG server, supply the subscription as a Proxmox Authorized Reseller and track renewals.
Monitoring and support
We monitor mail flow, queues and filter results and respond to undelivered messages and false positives. Our support line is open 24/7. We prioritize requests by business impact. Proxmox subscription support is vendor support.
Training
We give your IT team hands-on training in rule management, quarantine and message tracking. We set the training content and duration according to the project scope.
Proxmox Mail Gateway features
Multi-layer spam filter
SpamAssassin, greylisting, SPF, DNS blocklists and SURBL checks give every message a spam score.
Virus and malware scanning
The integrated ClamAV engine scans attachments and message content for viruses, trojans and malware.
Recipient verification
Messages to non-existent addresses are rejected at the SMTP stage, which spares the server unnecessary load.
Object-based rule system
You define flexible rules and actions based on sender, recipient, time and content conditions.
Message tracking center
You trace every step of a message, from receipt to delivery, in the logs of the last four weeks.
High-availability cluster
With several PMG nodes the configuration stays in sync, and mail keeps flowing when one node stops.
Use cases
Protecting Exchange or an on-premises mail server
Put a central filter layer in front of the mail server you host yourself.
Multi-domain setups
Protect and manage the domains of group companies from a single gateway.
Reducing phishing risk
Stop messages with spoofed senders and malicious links before they reach the user's mailbox.
Outbound mail control
Filter outgoing messages too and protect the reputation of your domain.
Zimbra server protection
Put a central spam, virus and phishing filter in front of the Zimbra mail server.
Proxmox Mail Gateway with Zimbra
For organizations that use a Zimbra mail server, we install PMG in front of Zimbra. Incoming email reaches PMG first. PMG forwards each filtered message to the Zimbra server, which is set as the Default Relay. According to the Proxmox documentation, to filter outgoing email as well, the mail server sends all outgoing messages through PMG (smarthost, port 26 by default). According to the Zimbra documentation, this relay host is set on the MTA tab of the administration console or with the zimbraMtaRelayHost attribute.
- MX record: We point your domain’s MX record to PMG.
- Incoming flow: In PMG we define the domain as a relay domain and the Zimbra server as the Default Relay.
- Outgoing flow: In Zimbra we set PMG as the relay MTA for external delivery.
- Recipient verification: We reject messages to non-existent addresses at the SMTP stage.
- Quarantine: Users see their spam quarantine and daily spam report in PMG.
Proxmox Mail Gateway subscription levels
Community
For test, lab and learning environments.
- Full feature set and stable updates
- No Proxmox technical support tickets
Basic
For teams that need support now and then.
- A limited number of support tickets per year via the Proxmox Customer Portal
Standard
For day-to-day production operations.
- More support tickets
- Shorter first response time
- Remote support via SSH and HTTPS
- Offline key activation
Premium
For organizations where email is critical.
- Unlimited support tickets
- Shortest first response time
- Remote support
A subscription is bought separately for each Proxmox Mail Gateway server (host). Each subscribed server covers an unlimited number of users and protected domains. The software features are the same at every level; the levels differ in support scope.
Support in the subscription levels is Proxmox vendor support. In Synchron support, our support line takes your request and prioritises it by business impact. Request a quote for the right level and price.
Our Solution Partners
Technologies we use
Microsoft Exchange
Microsoft 365
Zimbra
Frequently asked questions
What is Proxmox Mail Gateway?
Proxmox Mail Gateway is an open-source email security gateway that runs between your firewall and your mail server. It filters spam, viruses and phishing messages before they reach users.
Which mail servers does Proxmox Mail Gateway work with?
PMG works with mail servers that use standard SMTP. It can sit in front of servers such as Microsoft Exchange, Zimbra, Postfix and Lotus Domino.
Do I need PMG if I use Microsoft 365 or Google Workspace?
These platforms have their own filters; PMG works together with them as an additional security layer. Synchron deploys and supports PMG in front of the cloud mail service for organizations that use Microsoft 365 and Google Workspace. Organization-specific rules, central quarantine and message tracking are the benefits of this setup; we review your environment together and design the right mail flow.
Is Proxmox Mail Gateway free?
Yes. PMG is open source and free to use under the GNU AGPLv3 license. A subscription provides enterprise updates and, depending on the level, Proxmox technical support.
Is the Proxmox Mail Gateway license based on the number of users?
No. The subscription is bought per PMG server; the number of users and domains is unlimited.
What happens if a legitimate email is blocked?
Instead of being deleted, messages marked as spam can be kept in a spam quarantine that users can access. Users see their quarantine in the daily spam report and release their message; Synchron also tunes the rules to reduce false positives.
Can I track where an email went with PMG?
Yes. The message tracking center shows every step of a message, from receipt to the filtering result and delivery.
Can PMG run without interruption?
Yes. A high-availability cluster is built with several PMG nodes; when one node stops, the other keeps the mail flowing.
We use Zimbra; how is PMG set up?
We point the MX record to PMG. PMG forwards filtered email to the Zimbra server set as the Default Relay. For outgoing email we set PMG as the relay MTA for external delivery in Zimbra. We first test the change with a test domain.
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Let's discuss your project
Tell us what you need and we will match you with the right team. For urgent issues, call our support line.