You can write perfect emails to a perfect list and still get zero replies, because none of them reached the inbox. Deliverability is the unglamorous foundation under all of cold email, and it's the thing most founders learn about only after their domain reputation is already damaged. Here are the fundamentals, in order.

Authenticate your domain

SPF, DKIM, and DMARC are non-negotiable. They tell mailbox providers your mail is legitimately from you. Without them, you're starting in the spam folder. Set these up before you send a single cold email.

Don't send cold mail from your primary domain

If you blast cold outreach from your main company domain and it gets flagged, you can poison the deliverability of your normal business email too. Use a separate sending domain (often a close variant) dedicated to outreach, so your core domain stays clean.

Warm up new domains and mailboxes

A brand-new domain that suddenly sends 200 cold emails looks exactly like spam. Ramp volume gradually over weeks so providers learn to trust you. New mailboxes need the same patience.

Verify before you send

Bounces are one of the fastest ways to wreck a sender reputation. Verify email addresses before sending and drop the invalid ones. A clean list with a low bounce rate keeps you in the inbox.

Keep volume sane and content human

Low daily volume per mailbox, real personalization, no spammy phrases or heavy links, and a working unsubscribe. Mailbox providers reward mail that looks like a person wrote it to another person, which, conveniently, is also what gets replies.

Watch the signals

Rising bounces or falling open rates are early warnings that your reputation is slipping. Slow down, clean the list, and check your authentication before pushing more volume.

How Sigora helps

Sigora verifies every contact before you get it, and it's free if nothing is found, so you're never building outreach on stale or guessed addresses. You send through your own tools and keep control of your domain and deliverability; Sigora just makes sure the list you're working from is clean.