ZeroSpams

Email deliverability setup

Deliverability is whether your emails reach the inbox rather than spam or nowhere. It depends on how your domain is set up, how you send, and how recipients react, and most of it can be set up right from the start.

Updated · 2 min read · By the ZeroSpams team

The short answer

Email deliverability setup puts in place everything mailbox providers look at: SPF, DKIM and DMARC; separate domains or subdomains for everyday, transactional and marketing email; correct reverse DNS; one-click unsubscribe for marketing [3]; and clean lists. It meets the Gmail and Outlook sender requirements [1][2] and gives your email the best chance of reaching the inbox.

What’s included

  • Authentication for every sender: SPF, DKIM and DMARC, aligned.
  • Separate sending streams: everyday email, website and transactional email, and marketing, so one can’t harm the others.
  • Reverse DNS and TLS for any server you run yourself.
  • One-click unsubscribe and a visible unsubscribe link on marketing email [3][1].
  • List hygiene: removing invalid and risky addresses before sending.
  • Monitoring tools set up, including Google Postmaster Tools, so you can see your reputation.

How we do it

  1. Map what you send, from where, and to whom.
  2. Design the domain and subdomain setup.
  3. Configure authentication, DNS and sending services.
  4. Test inbox placement with real providers.
  5. Hand over a one-page guide to keeping it healthy.

What the big providers expect

Google asks every sender to authenticate their email and keep spam complaints low, and senders of 5,000+ messages a day to Gmail must have SPF, DKIM and DMARC, offer one-click unsubscribe on marketing mail, and keep reported spam below 0.3% [1]. Microsoft has required SPF, DKIM and DMARC for high-volume senders to Outlook.com since May 2025 [2]. Meeting these is the starting point for deliverability, not the finish.

Improving deliverability you already have

If your emails are already going to spam, start with fixing emails going to spam or a deliverability audit. This service is best when setting up a new domain, a new tool, or a fresh start.

Common questions

Why separate domains or subdomains?

So a marketing campaign that draws complaints can’t hurt the reputation of the domain your quotes and invoices come from.

Does this apply if we send small volumes?

Yes. The thresholds decide what’s mandatory, but providers judge every sender on authentication and reputation.

What is one-click unsubscribe?

A standard email header that lets people unsubscribe with one click from their mail app, without visiting a page [3]. Gmail requires it for bulk marketing mail [1].

Sources

Numbers in this guide come from these studies and publications. Links open the original.

  1. Email sender guidelines FAQGoogle Workspace Admin Help (Gmail)Requirements for senders of 5,000+ messages a day to Gmail since February 2024; stricter enforcement, including rejections, since November 2025.
  2. Strengthening Email Ecosystem: Outlook’s New Requirements for High-Volume SendersMicrosoft Defender for Office 365 blog, Microsoft Tech Community, 2025Since 5 May 2025: SPF, DKIM and DMARC required for domains sending 5,000+ emails a day to Outlook.com, Hotmail and Live.
  3. RFC 8058: Signaling One-Click Functionality for List Email HeadersIETF, 2017