Deliverability and Warming Up

Authentication decides whether your mail is accepted. Reputation decides where it lands. These are different problems, and fixing the first does not fix the second.

This guide covers what to expect from a new sending setup, how to warm it up, and what to do when campaigns land in spam.

Correct configuration is the starting line, not the finish

Once SPF, DKIM and DMARC pass, you have proven you are who you say you are. You have not yet given any mailbox provider a reason to deliver your mail to the inbox.

A new sending setup has no history. Providers such as Gmail decide placement largely on how recipients have responded to your mail in the past, and for a new sender there is no past. Their default treatment of an unknown sender mailing a large number of their users is the spam folder. This is normal and it is not a fault in your configuration.

What actually determines placement

In roughly the order that matters:

1. Engagement. Opens, clicks, replies, and messages moved out of spam. Recipients who interact with your mail are the strongest positive signal there is.
2. Complaints. Recipients clicking “report spam”. The strongest negative signal, and it takes very few to cause damage.
3. Invalid addresses. Mailing addresses that do not exist, repeatedly. See Bounce processing.
4. Consistency. A steady volume on a predictable schedule builds reputation. Long silences followed by large bursts do the opposite.
5. Content and links. Matters, but far less than most people assume. Content rarely rescues a sender with poor engagement, and rarely sinks one with good engagement.

Notice that four of the five are properties of your list and your sending pattern, not of your server.

Warming up

The goal is to build a history of engaged recipients before you send at volume.

Start with your most engaged recipients. If you have existing data on who opens your mail, send to them first. If you do not, start with your most recently acquired subscribers, who are the most likely to remember signing up.

Start small and increase gradually. A workable schedule:

Days	Volume per day
1 to 2	50 to 100
3 to 4	200
5 to 6	500
7 to 8	1,000
9 onward	Roughly double every two days while engagement holds

Watch engagement, not just volume. If open rates drop as you scale, stop increasing and hold at the current level until they recover. Pushing through a declining trend is how a warm up turns into a reputation problem.

Keep sending. Reputation decays. A sender who mails weekly maintains it. A sender who mails once a quarter starts close to cold each time.

Sending your entire list on day one is the single most common cause of a first campaign landing in spam. It is also the hardest mistake to recover from, because the poor engagement from that send becomes the history everything afterwards is judged against.

Set up Google Postmaster Tools

If a meaningful share of your recipients are on Gmail, and for most senders they are, this is the most useful diagnostic available and it is free.

1. Go to postmaster.google.com and sign in
2. Add your sending domain
3. Publish the TXT record it gives you to verify ownership

Once it has data, it shows your domain reputation, IP reputation, spam complaint rate, and authentication results, as Gmail sees them. Nothing else tells you what Gmail actually thinks of you.

It needs volume before it shows anything. Below a few hundred messages a day to Gmail, the dashboards stay empty. That is a limitation of the tool, not a sign of a problem.

List quality

The fastest way to damage a new sending setup is to mail a list that has not been used in a long time, or one whose provenance you are unsure of.

Before mailing an old or imported list, run it through an email verification service. It costs very little and removes the invalid addresses that would otherwise generate bounces and harm your reputation.

Never buy or rent lists. Recipients who did not ask to hear from you complain at rates that make recovery extremely difficult, and no amount of correct configuration compensates.

Segment by engagement. Recipients who have not opened anything in a year are dragging your averages down. Either run a dedicated re-engagement campaign for them or stop mailing them.

When a campaign lands in spam

Work through this in order.

Confirm authentication passes. Send yourself a test, open it in Gmail, choose Show original, and check that SPF, DKIM and DMARC all show PASS. If any fail, stop and fix that first.

Check Postmaster Tools for your domain reputation and complaint rate. A complaint rate above 0.3 percent explains spam placement on its own.

Look at the list, not the server. How was it built, when was it last mailed, and have those recipients engaged before?

Look at the sending pattern. Was this a large send from a setup with little history? Did a long gap precede it?

Then look at content. Image-heavy templates with little text, link shorteners, and unfamiliar link domains all contribute. Using your own tracking domain addresses the last of these.

What we handle and what you handle

We handle the sending infrastructure: the outbound path, the sending IPs and their reverse DNS, the platform, and monitoring. If our infrastructure is blocklisted or misconfigured, that is ours to fix, and you can open a ticket at any time to have us check it.

You handle the list, the content, the sending schedule, and the relationship with your recipients. These determine the large majority of your placement outcomes.

When you open a deliverability ticket, the most useful thing you can include is the full Show original output from a message that landed in spam. It tells us in one step what Gmail concluded about the message, and it is usually the difference between a same day answer and several rounds of questions.