EMAIL DELIVERABILITY
Authentication decides whether your mail is allowed to claim it is from you. Deliverability decides whether anyone actually receives it, and the two are related but not the same question.
A domain can pass every authentication check and still have its invoices filtered without a trace, because reputation, sending patterns and content all matter and none of them produce an error message.
This guide covers what receiving servers are actually deciding, why testing it yourself proves nothing, and how to diagnose mail that stopped arriving when nothing is logged anywhere.
In this guide you will learn:
Connection, authentication, reputation, content, in that order.
Domain and IP, engagement, complaints, and what resets it.
Internal mail bypasses the checks. What to test instead.
Marketing, transactional and correspondence do not belong together.
What the codes mean and which ones you can act on.
Which ones matter, how to check, and how delisting works.
No errors, fewer replies. Where to look and in what order.
Warm-up, volume changes, and what breaks it again.
Chapter 1
Connection, authentication, reputation, content, in that order.
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guide-bodies/<body>.html and rebuild.
Chapter 2
Domain and IP, engagement, complaints, and what resets it.
This chapter is not written yet. Drop the prose into
guide-bodies/<body>.html and rebuild.
Chapter 3
Internal mail bypasses the checks. What to test instead.
This chapter is not written yet. Drop the prose into
guide-bodies/<body>.html and rebuild.
Chapter 4
Marketing, transactional and correspondence do not belong together.
This chapter is not written yet. Drop the prose into
guide-bodies/<body>.html and rebuild.
Chapter 5
What the codes mean and which ones you can act on.
This chapter is not written yet. Drop the prose into
guide-bodies/<body>.html and rebuild.
Chapter 6
Which ones matter, how to check, and how delisting works.
This chapter is not written yet. Drop the prose into
guide-bodies/<body>.html and rebuild.
Chapter 7
No errors, fewer replies. Where to look and in what order.
This chapter is not written yet. Drop the prose into
guide-bodies/<body>.html and rebuild.
Chapter 8
Warm-up, volume changes, and what breaks it again.
This chapter is not written yet. Drop the prose into
guide-bodies/<body>.html and rebuild.
Check yours
Everything in this guide, checked on your domain in about ten seconds. Free, no account, every finding shown in full.