Why deliverability should decide which email platform a growing business chooses

Photo: Dylan Gillis / Unsplash

A campaign that took a fortnight to prepare goes out, the dashboard reports it as sent, and two days later the sales team is asking why no customer has mentioned it. A few test addresses later, the explanation appears: a large share of the messages went to junk folders, and some were never accepted at all.

Businesses in that position often turn to published comparisons of email marketing software and give every criterion equal weight. Once a list runs to thousands of contacts, deliverability should count for more than the rest, because a message that never reaches the inbox earns nothing from a low price or a good editor.

What Gmail and Yahoo now require from bulk senders

In early 2024, Google and Yahoo began enforcing stricter rules for bulk senders. The requirements are now the baseline for any organisation sending marketing email at volume: authenticated sending domains through SPF and DKIM, a published DMARC policy, a working one-click unsubscribe, and a spam complaint rate kept under the thresholds the providers publish. Microsoft has since moved Outlook in the same direction for high-volume senders.

The techniques themselves date back years. Since 2024 they have been conditions of delivery, so if your business sends from an unauthenticated domain, your campaigns now meet filtering that a good sender history no longer offsets.

The unsubscribe link has become a technical standard

The one-click requirement refers to a specific mechanism. RFC 8058, the internet standard for one-click unsubscription, defines a List-Unsubscribe-Post header that lets the recipient’s mail software unsubscribe them with a single action, without visiting a confirmation page. The standard also requires both unsubscribe headers to be covered by a valid DKIM signature, so that the mechanism cannot be forged.

The platform you choose should add these headers to every marketing message automatically and process the resulting requests without manual work from your team. To check, ask the vendor to send a test message to an address you control and open the full message headers, where both the List-Unsubscribe and the List-Unsubscribe-Post fields should appear, and confirm that the DKIM signature on that message names your own sending domain.

Data protection obligations stay with the business

Responsibility for the list stays with your business whichever platform holds it. Under the UK data protection rules for businesses, as GOV.UK summarises them, customer information must be kept secure, accurate and up to date, people must be told how their data will be used, and businesses must respond to requests to access, correct or delete it. Each of those duties has a direct counterpart in an email platform.

Accuracy is the one most closely tied to deliverability. Addresses that bounce repeatedly, or that have shown no activity for years, are hard to square with the duty to keep records accurate and up to date, and they are also a warning sign to mailbox providers, which read a high bounce rate as evidence that a sender does not maintain its list. A platform that suppresses hard bounces automatically and makes it simple to find inactive contacts serves both purposes. On security, user permissions that limit who in your organisation can export the full list, together with a log of every export, reduce the risk that a departing employee leaves with the customer database, and they give you evidence of the controls in place if the regulator ever asks.

Requests from individuals need a clear route too: your team should be able to find, export and delete one person’s record without raising a ticket with the vendor.

Questions to put to every vendor

A shortlist built on these points is easier to test than one built on feature lists. Ask each vendor to show the domain authentication set-up for a new account, a live example of the one-click unsubscribe header, the dashboard that reports complaint and bounce rates, and the process for exporting or deleting a single contact’s data. Anything a vendor cannot show on the call deserves a written answer before the contract is signed.