Inbound PMG + SmarterMail Enterprise + Multi-Gateway Outbound. Kept Clean, Blacklist-Proof & Built to Deliver.
Standard hosts and cloud servers break email deliverability by delivering directly to and sending directly from the same server IP—where a single noisy neighbor on a cloud subnet can land your domain on blacklists overnight.
Since 2007, GreenTree has architected email as a true 3-tier relay-isolated system: we never deliver directly to or send directly from our SmarterMail Enterprise server (east.greentreemail.com). All inbound mail is scrubbed first by our dedicated Inbound Proxmox Mail Gateway (mx.greentreemail.com), and all outbound mail routes through multiple dedicated outbound relay gateways—keeping the SmarterMail vault as clean as can be. Even better: every GreenTree Cloud Hosting plan (starting at $99/mo) includes 1 user account on our SmarterMail Enterprise plan, and additional accounts ($6–$18/mo) can always be added with full Autodiscover, IMAP, SMTP, POP3, Webmail, Mailing Lists, and DMARC support.
284,941 of 443,136 inbound envelopes (90d) blocked at mx.greentreemail.com (up to 75.8% in 24h peaks · 1.21s avg scan).
6 Combined Outbound Gateways across 3 providers (28,854 relayed in 58.7d · 2048-bit DKIM) — never sent directly from SmarterMail.
Every GreenTree Hosting plan (even at $99/mo) includes 1 SmarterMail Enterprise user account; add more at $6–$18/mo.
925+ active mailboxes & aliases (290+ GB vault) · Autodiscover, IMAP, SMTP, POP3, Webmail, Lists & strict SPF/DKIM/DMARC.
Three SmarterMail Enterprise Tiers — Relay-Isolated by Inbound PMG & Multiple Outbound Gateways
Every GreenTree Cloud Hosting plan (starting at $99/mo) includes 1 user account on our SmarterMail Enterprise plan at no additional charge, and additional mailboxes can always be added at $6 to $18/month (existing GreenTree mailbox customers keep their grandfathered monthly rates on active accounts). Every mailbox includes Autodiscover, IMAP, SMTP, POP3, Enterprise Webmail, 2048-bit DKIM, SPF/DMARC alignment, and white-glove migration.
SmarterMail Enterprise Core
Operational staff, field technicians, and role accounts requiring clean, ad-free corporate email with relay-isolated inbound PMG and multi-gateway outbound delivery.
- Inbound mail scrubbed by dedicated Proxmox Mail Gateway (mx.greentreemail.com) — never delivered directly to SmarterMail
- Outbound mail routed through multiple dedicated outbound relay gateways — never sent directly from the SmarterMail server
- Zero-touch Autodiscover for Outlook, Apple Mail, iPhone, Android & Thunderbird + Enterprise Webmail
- Full SPF, DKIM (2048-bit), and DMARC alignment engineered by our team
SmarterMail Enterprise Business & Lists
Growing teams, project managers, and business owners needing 50 GB storage, enterprise mailing lists, shared calendars/contacts, and relay-isolated deliverability (1 account included free with any $99+ GreenTree Cloud Hosting plan).
- 1 user account on our SmarterMail Enterprise plan is included free with every GreenTree Hosting plan (even at $99/mo)
- Enterprise Mailing Lists, domain aliases, shared calendars/contacts (CalDAV/CardDAV), and Autodiscover client setup
- Full 3-tier isolation: Inbound PMG Server → Isolated SmarterMail Vault → Multiple Outbound Relay Gateways
- White-glove mailbox migration from Microsoft 365, Google Workspace, GoDaddy, or legacy IMAP
SmarterMail Enterprise Executive & Archival Vault
Legal, financial, real estate, and industrial executives requiring deep 100 GB mailbox capacity, enterprise mailing lists, and retention governance.
- 100 GB primary NVMe mailbox allocation with server-level message retention and journaling policies
- Multi-gateway outbound IP reputation governance, strict DMARC enforcement & custom rDNS/PTR verification
- Priority administrative support for employee onboarding/offboarding and litigation holds
- Continuous DNSBot.app monitoring of your domain’s MX, SPF, DKIM, and DMARC records
How Our 8-Stage Proxmox Mail Gateway Scrubs Every Message Before It Reaches Your Team
Instead of letting spam and ransomware land in a user’s Junk folder where a single click can compromise your network, our perimeter gateway inspects and drops threats at the network edge.
Postscreen Protocol Checks & Real-Time Blackhole Lists
External mail never delivers directly to our SmarterMail server. Every inbound connection terminates first at our dedicated Proxmox Mail Gateway (mx.greentreemail.com), dropping botnets and checking Spamhaus, Barracuda, and RBL feeds.
Strict TLS 1.3, SPF, 2048-Bit DKIM, DMARC & ClamAV
Our Inbound PMG cluster verifies sender SPF policies, validates 2048-bit DKIM signatures, enforces DMARC alignment, and scans attachments for ransomware and phishing before a message ever leaves the gateway.
Clean Internal Delivery to east.greentreemail.com
Only verified clean mail is passed internally to our SmarterMail Enterprise server—supporting zero-touch Autodiscover, IMAP, SMTP, POP3, Enterprise Webmail, CalDAV/CardDAV, and Enterprise Mailing Lists while keeping the server completely clean.
Never Sent Directly From SmarterMail — Blacklist-Proof Delivery
Outbound mail is never sent directly from the SmarterMail server. Instead, it routes through multiple dedicated outbound relay gateways with strict DKIM/DMARC signing—delivering reliably even across cloud platforms where other hosts get blocked on blacklists.
Microsoft 365 / Shared Host Email vs. GreenTree Proxmox + SmarterMail
| Evaluation Factor | Hyperscaler Per-Seat Tax / Shared cPanel Mail | GreenTree Proxmox + SmarterMail Enterprise |
|---|---|---|
| 3-Year Cost for a 25-Person Company | ✗ $10,800 – $27,000+ on Microsoft 365 / Google Workspace once per-seat add-ons, archiving, and security tiers are tacked on. | ✓ $5,400 – $9,000 total ($6 to $10/mailbox/mo, with 1 Enterprise account included free on any $99+ hosting plan) and Proxmox 8-stage gateway security included. |
| Inbound & Outbound Relay Isolation | ✗ Shared cPanel/VPS hosts deliver and send directly from the web/mailbox server IP—where noisy cloud neighbors constantly put whole IP blocks on blacklists. | ✓ Full 3-tier architecture: Inbound PMG server (mx.greentreemail.com) → Isolated SmarterMail Enterprise vault (east.greentreemail.com) → Multiple dedicated outbound relay gateways. |
| Inbound Spam & Phishing Defense | ✗ Basic default filtering unless you pay extra per user for Defender / advanced threat add-ons. | ✓ Dedicated Proxmox Mail Gateway 8.2.0 (mx.greentreemail.com) eliminating 64.3% of all inbound envelopes at the perimeter (284,941 of 443,136 in 90 days; up to 75.8% during active spam waves) with 19.7% dropped at the TCP/Postscreen/SPF handshake and 1.21s average scan latency. |
| Support When an Important Email Goes Missing | ✗ Impossible to get a human engineer to trace a real-time SMTP log in Microsoft 365 or Google. | ✓ Call or email our Southbury, CT desk and we will pull the exact line-by-line Proxmox/SmarterMail/Outbound Gateway SMTP transaction log in minutes. |
Frequently Asked Questions About Enterprise Email
Is an email account really included with your $99/mo and $199/mo Cloud Hosting plans?
Yes. Even on our $99/mo GreenTree Core Cloud plan (as well as our $199/mo Core Cloud + Management plan and custom environments), 1 user account on our SmarterMail Enterprise plan is included at no extra cost. Additional mailbox accounts ($6–$18/mo) can always be added anytime as your team grows.
Why do you never deliver directly to—or send directly from—the SmarterMail Enterprise server?
Many cloud and VPS providers suffer from whole IP ranges landing on spam blacklists because of noisy neighbors. By placing a dedicated Inbound Proxmox Mail Gateway (mx.greentreemail.com) in front of our SmarterMail Enterprise server and routing all outgoing mail through multiple dedicated outbound relay gateways, our SmarterMail server is never exposed to direct public SMTP delivery or sending. That keeps the mailbox server as clean as can be and ensures robust, high-reputation delivery.
What protocols and features are supported on your SmarterMail Enterprise deployment?
Our SmarterMail Enterprise deployment (east.greentreemail.com) supports zero-touch Autodiscover, IMAP, SMTP, POP3, lightning-fast Enterprise Webmail, CalDAV/CardDAV shared calendars and contacts, Enterprise Mailing Lists, and full SPF, 2048-bit DKIM, and DMARC authentication. You can also mix and match $6/mo (25GB), $10/mo (50GB + Mailing Lists), and $18/mo (100GB Archival Vault) tiers on the same domain.
Do you migrate our existing mailboxes and configure SPF, DKIM, and DMARC for us?
100% included. We perform server-to-server mailbox migrations from Microsoft 365, Google Workspace, GoDaddy, or legacy IMAP, help your team connect via Autodiscover/IMAP/Webmail, and engineer and monitor your SPF, 2048-bit DKIM, and DMARC records directly.
Read Our Production SmarterMail Administration & Migration Runbooks
See the exact 3-tier relay isolation architecture and two-pass mailbox migration checklists we use to move companies off Microsoft 365, Google Workspace, and legacy hosts without breaking Outlook, iPhones, or DMARC: