Forem: Dhiraj Chatpar

DKIM SPF DMARC: Complete Email Authentication for PostMTA

Dhiraj Chatpar — Wed, 20 May 2026 10:42:17 +0000

DKIM, SPF & DMARC: Complete Email Authentication Setup for PostMTA

Email authentication is non-negotiable for deliverability. Here's how to configure it properly with PostMTA.

DNS Records You Need

SPF Record (TXT record for your sending domain):

v=spf1 include:_spf.postmta.com ~all

DKIM Record (TXT record — PostMTA generates the key):

postmta._domainkey IN TXT ( "v=DKIM1; k=rsa; p=YOUR_PUBLIC_KEY" )

DMARC Record (TXT at _dmarc.yourdomain.com):

v=DMARC1; p=quarantine; rua=mailto:dmarc@yourdomain.com; pct=100

PostMTA Authentication Features

Automatic DKIM signing — Per-domain keys, rotated automatically
SPF alignment — Strict alignment mode available
DMARC reporting — Aggregate reports in dashboard
Failover handling — Route around ISP blocks

Testing Your Setup

Use these tools to verify:

mail-tester.com — Full spam score analysis
mxtoolbox.com — DNS record checks
postmta.com/dashboard — Delivery analytics

Configure PostMTA authentication →

How to Set Up PostMTA: Complete Installation Guide

Dhiraj Chatpar — Wed, 20 May 2026 10:38:12 +0000

How to Set Up PostMTA: Complete Installation Guide

PostMTA is the enterprise-grade email delivery platform built on KumoMTA. This guide walks through a production-ready setup.

Prerequisites

Ubuntu 22.04 or Debian 12
2GB+ RAM, 20GB+ disk
Static IP with reverse DNS configured
Domain with DNS access

Step 1: Install PostMTA

# Download the installer
curl -sSL https://postmta.com/install | bash

# Or via Docker
docker run -d postmta/postmta:latest

Step 2: Configure Your Domain

Set up your sending domain with proper DKIM, SPF, and DMARC records.

Step 3: Configure Bounce Processing

PostMTA monitors bounce addresses and automatically suppresses invalid recipients.

Step 4: Warm Up Your IPs

Start with 1K emails/day and ramp up 20% daily to build sender reputation.

Monitoring

PostMTA dashboard shows delivery rates, bounces, and reputation metrics in real-time.

Get started at postmta.com →

Email Bounce Rate: How to Keep It Under 2% with PostMTA

Dhiraj Chatpar — Wed, 20 May 2026 10:28:32 +0000

Keeping Your Email Bounce Rate Under 2% with PostMTA

A bounce rate above 2% damages your sender reputation and lands you in spam folders. Here's how to fix it.

Hard Bounces vs Soft Bounces

Hard bounces: Invalid email addresses — permanently undeliverable. PostMTA suppresses these automatically within hours.

Soft bounces: Temporary failures (mailbox full, server down). PostMTA retries 72 hours then suppresses if still failing.

PostMTA Bounce Processing Features

Instant suppression — Hard bounces suppressed immediately
Bounce classification — Identifies mailbox full vs domain no longer exists
Feedback loop integration — FBL from major providers (Gmail, Microsoft)
List hygiene scoring — Scores subscribers by engagement

Best Practices

Verify emails at signup (API check before adding to list)
Remove addresses that soft-bounce 3+ times
Monitor your sender score at postmta.com/dashboard
Use dedicated IPs for different list segments

PostMTA handles bounces automatically →

Email Bounce Rate: How to Keep It Under 2% with PostMTA

Dhiraj Chatpar — Wed, 20 May 2026 10:21:56 +0000

Keeping Your Email Bounce Rate Under 2% with PostMTA

A bounce rate above 2% damages your sender reputation and lands you in spam folders. Here's how to fix it.

Hard Bounces vs Soft Bounces

Hard bounces: Invalid email addresses — permanently undeliverable. PostMTA suppresses these automatically within hours.

Soft bounces: Temporary failures (mailbox full, server down). PostMTA retries 72 hours then suppresses if still failing.

PostMTA Bounce Processing Features

Instant suppression — Hard bounces suppressed immediately
Bounce classification — Identifies mailbox full vs domain no longer exists
Feedback loop integration — FBL from major providers (Gmail, Microsoft)
List hygiene scoring — Scores subscribers by engagement

Best Practices

Verify emails at signup (API check before adding to list)
Remove addresses that soft-bounce 3+ times
Monitor your sender score at postmta.com/dashboard
Use dedicated IPs for different list segments

PostMTA handles bounces automatically →

DKIM SPF DMARC: Complete Email Authentication for PostMTA

Dhiraj Chatpar — Wed, 20 May 2026 10:10:45 +0000

DKIM, SPF & DMARC: Complete Email Authentication Setup for PostMTA

Email authentication is non-negotiable for deliverability. Here's how to configure it properly with PostMTA.

DNS Records You Need

SPF Record (TXT record for your sending domain):

v=spf1 include:_spf.postmta.com ~all

DKIM Record (TXT record — PostMTA generates the key):

postmta._domainkey IN TXT ( "v=DKIM1; k=rsa; p=YOUR_PUBLIC_KEY" )

DMARC Record (TXT at _dmarc.yourdomain.com):

v=DMARC1; p=quarantine; rua=mailto:dmarc@yourdomain.com; pct=100

PostMTA Authentication Features

Automatic DKIM signing — Per-domain keys, rotated automatically
SPF alignment — Strict alignment mode available
DMARC reporting — Aggregate reports in dashboard
Failover handling — Route around ISP blocks

Testing Your Setup

Use these tools to verify:

mail-tester.com — Full spam score analysis
mxtoolbox.com — DNS record checks
postmta.com/dashboard — Delivery analytics

Configure PostMTA authentication →

Email Bounce Rate: How to Keep It Under 2% with PostMTA

Dhiraj Chatpar — Wed, 20 May 2026 10:09:44 +0000

Keeping Your Email Bounce Rate Under 2% with PostMTA

A bounce rate above 2% damages your sender reputation and lands you in spam folders. Here's how to fix it.

Hard Bounces vs Soft Bounces

Hard bounces: Invalid email addresses — permanently undeliverable. PostMTA suppresses these automatically within hours.

Soft bounces: Temporary failures (mailbox full, server down). PostMTA retries 72 hours then suppresses if still failing.

PostMTA Bounce Processing Features

Instant suppression — Hard bounces suppressed immediately
Bounce classification — Identifies mailbox full vs domain no longer exists
Feedback loop integration — FBL from major providers (Gmail, Microsoft)
List hygiene scoring — Scores subscribers by engagement

Best Practices

Verify emails at signup (API check before adding to list)
Remove addresses that soft-bounce 3+ times
Monitor your sender score at postmta.com/dashboard
Use dedicated IPs for different list segments

PostMTA handles bounces automatically →

DKIM SPF DMARC: Complete Email Authentication for PostMTA

Dhiraj Chatpar — Wed, 20 May 2026 10:05:10 +0000

DKIM, SPF & DMARC: Complete Email Authentication Setup for PostMTA

Email authentication is non-negotiable for deliverability. Here's how to configure it properly with PostMTA.

DNS Records You Need

SPF Record (TXT record for your sending domain):

v=spf1 include:_spf.postmta.com ~all

DKIM Record (TXT record — PostMTA generates the key):

postmta._domainkey IN TXT ( "v=DKIM1; k=rsa; p=YOUR_PUBLIC_KEY" )

DMARC Record (TXT at _dmarc.yourdomain.com):

v=DMARC1; p=quarantine; rua=mailto:dmarc@yourdomain.com; pct=100

PostMTA Authentication Features

Automatic DKIM signing — Per-domain keys, rotated automatically
SPF alignment — Strict alignment mode available
DMARC reporting — Aggregate reports in dashboard
Failover handling — Route around ISP blocks

Testing Your Setup

Use these tools to verify:

mail-tester.com — Full spam score analysis
mxtoolbox.com — DNS record checks
postmta.com/dashboard — Delivery analytics

Configure PostMTA authentication →

PostMTA vs SendGrid: Enterprise Email Delivery Compared

Dhiraj Chatpar — Wed, 20 May 2026 10:04:09 +0000

PostMTA vs SendGrid: Which Handles Enterprise Email Better?

SendGrid charges $89+/month for 100K emails. PostMTA delivers the same volume for a fraction of the cost — running on your own infrastructure.

Key Differences

Cost at Scale

SendGrid 100K/month: ~$89/mo
SendGrid 1M/month: ~$890/mo
PostMTA: One-time setup + your cloud costs (~$20-50/mo for equivalent)

Control

SendGrid: You rely on their infrastructure, their limits, their decisions
PostMTA: You own everything. Full data, full control, no rate caps from third parties

Bounce Handling

SendGrid: 5-day bounce email address
PostMTA: Configurable per-list bounce rules, instant suppression

Authentication

Both support DKIM/SPF/DMARC
PostMTA lets you run dedicated IPs for sender reputation

When to Choose PostMTA

Sending 50K+ emails/month
Need white-label email infrastructure
Running multiple sender domains
Managing email for multiple clients (agencies)

When SendGrid Makes Sense

Low volume (<10K/month)
No technical team to manage MTA
Need instant API integrations

PostMTA → Start free trial

PostMTA vs PowerMTA: The Enterprise MTA Showdown

Dhiraj Chatpar — Wed, 20 May 2026 09:46:45 +0000

PostMTA vs PowerMTA: Enterprise MTA Compared

PowerMTA is the legacy enterprise standard. PostMTA is the modern replacement. Here's the honest comparison.

Pricing

	PowerMTA	PostMTA
License	$7,500+/year	Contact us
Setup	$5,000+ professional	Included
Support	Expensive tiers	Dedicated CSM
Updates	Extra cost	Included

PowerMTA's hidden costs add up fast.

Technical Comparison

Both handle millions of emails. Both support advanced bounce processing. But:

PostMTA: REST API, modern dashboard, Docker/K8s native
PowerMTA: Config files, third-party monitoring, legacy architecture

Why Enterprises Switch to PostMTA

Modern infrastructure — Kubernetes-native, Prometheus metrics
Better support — Dedicated engineer, not a ticket queue
Easier ops — Web UI vs config file management
Open-source foundation — KumoMTA means community-driven development

The Bottom Line

If you're paying $7.5K+/year for PowerMTA and managing it with config files, you owe it to your team to see what PostMTA offers.

Request a PostMTA demo →

DKIM SPF DMARC: Complete Email Authentication for PostMTA

Dhiraj Chatpar — Wed, 20 May 2026 09:33:47 +0000

DKIM, SPF & DMARC: Complete Email Authentication Setup for PostMTA

Email authentication is non-negotiable for deliverability. Here's how to configure it properly with PostMTA.

DNS Records You Need

SPF Record (TXT record for your sending domain):

v=spf1 include:_spf.postmta.com ~all

DKIM Record (TXT record — PostMTA generates the key):

postmta._domainkey IN TXT ( "v=DKIM1; k=rsa; p=YOUR_PUBLIC_KEY" )

DMARC Record (TXT at _dmarc.yourdomain.com):

v=DMARC1; p=quarantine; rua=mailto:dmarc@yourdomain.com; pct=100

PostMTA Authentication Features

Automatic DKIM signing — Per-domain keys, rotated automatically
SPF alignment — Strict alignment mode available
DMARC reporting — Aggregate reports in dashboard
Failover handling — Route around ISP blocks

Testing Your Setup

Use these tools to verify:

mail-tester.com — Full spam score analysis
mxtoolbox.com — DNS record checks
postmta.com/dashboard — Delivery analytics

Configure PostMTA authentication →

Email Bounce Rate: How to Keep It Under 2% with PostMTA

Dhiraj Chatpar — Wed, 20 May 2026 09:28:41 +0000

Keeping Your Email Bounce Rate Under 2% with PostMTA

A bounce rate above 2% damages your sender reputation and lands you in spam folders. Here's how to fix it.

Hard Bounces vs Soft Bounces

Hard bounces: Invalid email addresses — permanently undeliverable. PostMTA suppresses these automatically within hours.

Soft bounces: Temporary failures (mailbox full, server down). PostMTA retries 72 hours then suppresses if still failing.

PostMTA Bounce Processing Features

Instant suppression — Hard bounces suppressed immediately
Bounce classification — Identifies mailbox full vs domain no longer exists
Feedback loop integration — FBL from major providers (Gmail, Microsoft)
List hygiene scoring — Scores subscribers by engagement

Best Practices

Verify emails at signup (API check before adding to list)
Remove addresses that soft-bounce 3+ times
Monitor your sender score at postmta.com/dashboard
Use dedicated IPs for different list segments

PostMTA handles bounces automatically →

PostMTA vs PowerMTA: The Enterprise MTA Showdown

Dhiraj Chatpar — Wed, 20 May 2026 09:21:35 +0000

PostMTA vs PowerMTA: Enterprise MTA Compared

PowerMTA is the legacy enterprise standard. PostMTA is the modern replacement. Here's the honest comparison.

Pricing

	PowerMTA	PostMTA
License	$7,500+/year	Contact us
Setup	$5,000+ professional	Included
Support	Expensive tiers	Dedicated CSM
Updates	Extra cost	Included

PowerMTA's hidden costs add up fast.

Technical Comparison

Both handle millions of emails. Both support advanced bounce processing. But:

PostMTA: REST API, modern dashboard, Docker/K8s native
PowerMTA: Config files, third-party monitoring, legacy architecture

Why Enterprises Switch to PostMTA

Modern infrastructure — Kubernetes-native, Prometheus metrics
Better support — Dedicated engineer, not a ticket queue
Easier ops — Web UI vs config file management
Open-source foundation — KumoMTA means community-driven development

The Bottom Line

If you're paying $7.5K+/year for PowerMTA and managing it with config files, you owe it to your team to see what PostMTA offers.

Request a PostMTA demo →