Email deliverability

Deliverability is whether the email you send reaches the inbox rather than the spam folder or nothing at all. It is a separate question from whether the email was delivered, and a separate question again from whether it was any good. A well-written message from a domain nobody trusts goes to spam, and the report in your email platform will describe that send as a success.

In short

• Delivered means accepted by the server, not seen by the person.
• Reputation attaches to your domain and follows it everywhere.
• Complaints and dead addresses cost more than wording ever does.
• Send marketing from a subdomain so invoices are not caught in it.

Delivered is not the same as seen

The most useful thing to understand here is that your platform cannot see the outcome you care about.

When a message is accepted by Gmail or by Outlook, the sending platform records a delivery and stops learning anything. Where the message goes next is decided inside the receiving provider, and that decision is not reported back. A send can show ninety-nine per cent delivered while most copies sit in spam folders, and nothing in the interface would look different.

Which is why the useful signals are indirect. Clicks arriving from a send tell you people saw it. A collapse in open rate tells you something changed, without telling you what. Neither is a measurement of placement, and no honest tool offers one.

What Gmail and Outlook now require

Two of the largest mailbox providers have written down what they expect, which removes most of the guesswork.

From February 2024, senders posting more than five thousand messages a day to Gmail have had to authenticate with SPF and DKIM, publish a DMARC record, include a one-click unsubscribe alongside a visible unsubscribe link, and keep the spam rate reported in Google’s Postmaster Tools below 0.30 per cent, with 0.10 per cent given as the level to aim for. From May 2025, Outlook has applied a similar threshold, requiring high-volume domains to pass SPF and DKIM and publish DMARC, and routing non-compliant mail to the junk folder.

One detail in the Outlook rules is worth carrying away: once a domain has crossed the volume threshold, the requirements continue to apply even after the sending drops back below it. Reputation is not something you leave behind by sending less.

Most Philippine small businesses are nowhere near five thousand messages a day, and reading that as permission to skip the setup is the mistake. The same authentication is what keeps ordinary business mail out of junk folders today, it is configured once in your DNS records, and it takes effect long before anybody counts your volume.

Words you will hear

• Sender reputation. A running judgement, held by each provider, about mail from your domain and your sending servers.
• Hard bounce. The address does not exist. Remove it immediately.
• Soft bounce. A temporary refusal, such as a full mailbox.
• Spam trap. An address that exists only to catch senders using lists they should not have, including old addresses recycled by the provider.
• Spam rate. The proportion of delivered mail that recipients report.
• Warming up. Raising volume gradually on a new domain or platform so the sending pattern does not look sudden.
• Postmaster Tools. Google’s free view of how it currently sees your domain.

Reputation is earned by the list, not the copy

Almost every recovery from a deliverability problem is a change to who is receiving the mail rather than a change to what it says.

Providers are watching a pattern of behaviour. People who open, reply and click build the reputation. People who report, delete unread or never existed erode it. Because that is a ratio, keeping addresses that never respond actively harms the people who do, which is the opposite of the instinct to protect list size.

• Remove hard bounces at once. Repeatedly mailing an address that does not exist is one of the clearest bad signals available.
• Retire the permanently silent. Twelve months of no clicks means an address that costs you more than it returns.
• Never buy or scrape. Bought lists contain traps, and the damage lands on your domain, not on the seller.
• Raise volume gradually. A first send to eight thousand people from a domain that has never sent marketing looks exactly like a compromised account.

Deleting subscribers feels like undoing the work, so it rarely happens until something has already gone wrong. The point of email marketing is the people who respond, and they are the ones being quietly penalised by everybody on the list who does not.

Keep the invoices away from the marketing

The last piece is structural, and it is the one people regret skipping.

Your reputation is attached to the domain in the sending address. If that is the same domain your quotations, invoices and replies to customers leave from, then a campaign that goes badly follows your business correspondence into junk folders. That is an expensive way to learn the lesson, because the mail that stops arriving is the mail somebody is waiting for.

The standard arrangement is a subdomain kept for bulk sending, set up in the same place as your other hosting records. It builds its own reputation, it can be repaired without touching anything else, and every automated message from an email flow goes out through it. The mailboxes your business actually runs on stay on the main domain, which is the arrangement any competent email hosting setup starts from. The work is an afternoon, once, and it is only ever appreciated in hindsight.