Secure Mail Server Configuration & Anti-Spam Measures & Server Security Hardening
Budget: $10 – $30 USD
Server Configuration & Security Hardening
Objective:
Deploy a secure mail server environment with proper authentication, reputation safeguards, and inbound spam filtering to ensure outgoing emails are trusted and incoming spam/malware is blocked.
Scope of Work
1. Outgoing Email Configuration – Deliverability & Reputation
Install and configure a Mail Transfer Agent (MTA) (e.g., Postfix, Exim).
Set up and validate:
SPF (Sender Policy Framework)
DKIM (DomainKeys Identified Mail)
DMARC (Domain-based Message Authentication, Reporting, and Conformance)
Configure rDNS (reverse DNS) for the server IP.
Implement HELO/EHLO hostname matching.
Enable rate limiting and outbound spam protection (e.g., Postscreen, RBL checks).
Set proper envelope sender policies and bounce handling.
Configure FCrDNS (Forward-confirmed reverse DNS) for email legitimacy.
Set up feedback loops (FBL) with major providers (e.g., Gmail, Microsoft) if sending in volume.
Regularly check and monitor blacklist status (DNSBL, RBL).
2. Inbound Email Protection – Anti-Spam & Filtering
Install an inbound filtering system (e.g., SpamAssassin, Rspamd, or Amavis).
Use real-time blackhole lists (RBLs) and greylisting to block known spam sources.
Enable ClamAV or another anti-virus tool to scan attachments.
Configure SMTP banner compliance and anti-abuse settings.
Block spoofed and forged senders (e.g., SPF/DKIM failures).
Implement recipient verification to avoid backscatter spam.
Enable rate-limiting and throttling for inbound SMTP traffic.
Filter suspicious attachments (e.g., .exe, .js, macro-enabled docs).
3. Security Hardening
Secure mail ports (25, 465, 587) and enforce STARTTLS or SMTPS.
Harden access to mail server (e.g., disable plain-text auth, use SASL).
Enable firewall rules (e.g., UFW/iptables) to only allow necessary traffic.
Implement Fail2Ban or CrowdSec for brute-force protection.
Keep all components (MTA, spam filters, AV tools) regularly updated.
4. Monitoring & Alerts
Integrate monitoring tools (e.g., Zabbix, Prometheus, UptimeRobot).
Set up:
Mail queue monitoring
Blacklist monitoring
Delivery failure reports
Unusual volume alerts (spam bursts, relay attempts)
Enable logging of accepted/rejected mail and spam hits.
Deliverables:
Fully configured mail server (inbound & outbound)
SPF, DKIM, DMARC records tested and passing
TLS encryption enforced for mail transport
Spam filtering and AV scanning in place
Daily monitoring and alerting system active
Documentation of mail flow architecture and security policies
Remove all blacklisting for the server IP's
Objective:
Deploy a secure mail server environment with proper authentication, reputation safeguards, and inbound spam filtering to ensure outgoing emails are trusted and incoming spam/malware is blocked.
Scope of Work
1. Outgoing Email Configuration – Deliverability & Reputation
Install and configure a Mail Transfer Agent (MTA) (e.g., Postfix, Exim).
Set up and validate:
SPF (Sender Policy Framework)
DKIM (DomainKeys Identified Mail)
DMARC (Domain-based Message Authentication, Reporting, and Conformance)
Configure rDNS (reverse DNS) for the server IP.
Implement HELO/EHLO hostname matching.
Enable rate limiting and outbound spam protection (e.g., Postscreen, RBL checks).
Set proper envelope sender policies and bounce handling.
Configure FCrDNS (Forward-confirmed reverse DNS) for email legitimacy.
Set up feedback loops (FBL) with major providers (e.g., Gmail, Microsoft) if sending in volume.
Regularly check and monitor blacklist status (DNSBL, RBL).
2. Inbound Email Protection – Anti-Spam & Filtering
Install an inbound filtering system (e.g., SpamAssassin, Rspamd, or Amavis).
Use real-time blackhole lists (RBLs) and greylisting to block known spam sources.
Enable ClamAV or another anti-virus tool to scan attachments.
Configure SMTP banner compliance and anti-abuse settings.
Block spoofed and forged senders (e.g., SPF/DKIM failures).
Implement recipient verification to avoid backscatter spam.
Enable rate-limiting and throttling for inbound SMTP traffic.
Filter suspicious attachments (e.g., .exe, .js, macro-enabled docs).
3. Security Hardening
Secure mail ports (25, 465, 587) and enforce STARTTLS or SMTPS.
Harden access to mail server (e.g., disable plain-text auth, use SASL).
Enable firewall rules (e.g., UFW/iptables) to only allow necessary traffic.
Implement Fail2Ban or CrowdSec for brute-force protection.
Keep all components (MTA, spam filters, AV tools) regularly updated.
4. Monitoring & Alerts
Integrate monitoring tools (e.g., Zabbix, Prometheus, UptimeRobot).
Set up:
Mail queue monitoring
Blacklist monitoring
Delivery failure reports
Unusual volume alerts (spam bursts, relay attempts)
Enable logging of accepted/rejected mail and spam hits.
Deliverables:
Fully configured mail server (inbound & outbound)
SPF, DKIM, DMARC records tested and passing
TLS encryption enforced for mail transport
Spam filtering and AV scanning in place
Daily monitoring and alerting system active
Documentation of mail flow architecture and security policies
Remove all blacklisting for the server IP's