Deliverability

The most important distinction in this whole field is between delivery and deliverability. Delivery rate is the share of your mail the receiving server accepted rather than bounced. A message can sail through that test, get accepted with a 250 OK, and then be quietly filed in the spam folder. It was delivered, but it failed to land. Deliverability asks the harder question: of the mail that was accepted, how much actually reached the inbox?

This is why a 99% delivery rate can hide a deliverability disaster. The number that matters is inbox placement, the percentage of sent mail that lands in the inbox rather than spam. Most sending dashboards cannot see the spam folder, so strong deliverability has to be measured with seed tests and provider tools, not inferred from a clean bounce log.

No single switch controls deliverability; mailbox providers weigh several signals together. The big ones are:

• Authentication. SPF, DKIM, and DMARC are the entry ticket. Unauthenticated mail is increasingly filtered or rejected by default.
• Reputation. Your IP and domain reputation is the track record providers score you on, and it is the strongest lever of all.
• Engagement. Opens, clicks, and replies tell providers people want your mail; ignored mail and spam complaints tell them the opposite.
• List hygiene. Clean lists keep bounce rates and spam-trap hits low; stale lists do the reverse.
• Content and infrastructure. Spammy content, broken links, missing reverse DNS, and poor IP warmup all weigh against you.

The throughline is trust. Every one of these is a way for a mailbox provider to ask the same question: does this sender look like someone whose mail my users want?

Because your own platform cannot see whether mail landed in the inbox or spam, deliverability is measured indirectly. Inbox placement tests seed a list of monitored mailboxes across providers and report where each copy landed. Google Postmaster Tools exposes your Gmail domain reputation, spam rate, and authentication results. A feedback loop reports complaints from providers that offer one.

Industry benchmarks consistently put the global average inbox placement rate in the mid-80s percent, meaning roughly one in six legitimate marketing emails never reaches the inbox. Well-authenticated senders with clean lists and strong engagement routinely clear 90%, which is the realistic target rather than a perfect 100%.

The work is steady rather than dramatic: get authentication fully passing and aligned, send only to engaged recipients, clean bounces and inactive addresses regularly, warm new IPs and domains gradually, and keep complaints near zero. Each of these feeds reputation, and reputation feeds placement.

A practical starting point is to measure where you stand. Run your domain through the sender reputation checker for an authentication, DNS, and blacklist overview, then work through the deliverability guide to close the gaps it surfaces.