Server & Software Requirements
Port 25 Access Required: Your server must have unrestricted access to port 25 (SMTP) for verification to work. ISPs often block this to prevent spam.
Minimum & Recommended Specs
| Component | Minimum | Recommended |
|---|---|---|
| CPU | 2 vCPU | 4 vCPU+ |
| RAM | 2GB | 4GB+ |
| Storage | 20GB SSD | 50GB+ SSD |
| OS | Ubuntu 20.04+, CentOS 8+, Debian 11+ | |
Software Dependencies
- Node.js 18+ (required)
- MariaDB 10.5+ (required)
- Redis 6+ (required for Yahoo/AOL verification)
- Playwright Chromium (required for browser-based verification)
- PM2 (recommended for process management)
Tip: Use SSD storage and at least 4GB RAM for best performance on large lists.
Network & Port Requirements
| Port | Protocol | Purpose | Required |
|---|---|---|---|
| 25 | SMTP | Email verification via SMTP | Yes |
| 3306 | MySQL | MariaDB database connection | Yes |
| 6379 | Redis | Browser concurrency locking | Yes |
| 80 | HTTP | Web interface (redirect to HTTPS) | Recommended |
| 443 | HTTPS | Secure web interface | Recommended |
| 3001 | HTTP | Application server (custom port) | Yes |
| 993 | IMAPS | IMAP verification (outbound) | Optional |
VPS Provider Recommendations
Vsys.host
Port 25 Allowed
High Performance
24/7 Support
OVH.com
Port 25 Allowed
Global Network
DDoS Protection
Private-hosting.eu
Port 25 Allowed
Privacy Focused
EU Based
Contabo.com
Port 25 Allowed
Budget Friendly
High Resources
Vultr.com
Port 25 On Request
SSD Storage
Global Locations
Linode.com
Port 25 On Request
Developer Friendly
Great Support
Note: Always verify port 25 access before purchasing. Some providers require manual unblocking. Avoid AWS, Google Cloud, and Azure for mail servers (port 25 restrictions).