Before you buy more inboxes

On a recent consult, the team told me they were replacing their sending infrastructure every two weeks.

I wanted to know how they were deciding what needed replacing.

Buying on a schedule could mean taking working domains out of service. Meanwhile, a domain with poor results keeps running until its turn comes around.

What I wanted for them was peace of mind. Know which domains need help and have replacements ready. No morning spent checking each account.

I'd check results each week and keep an equal amount of sending capacity ready in reserve. And I'd set rules for when to rethink the campaign instead of buying more domains.

Decide what earns a replacement

Use 7-day windows, per campaign, and compare each sending domain's reply rate against that campaign's average.

Count human replies only. Leave out out-of-office replies. A holiday reply doesn't tell you whether someone liked the message.

My rotation rule is below 70% of campaign-average reply rate or below 1% reply rate.

For example, 2% campaign-average reply rate means a 1.4% rotation threshold. Domains below that threshold qualify under the relative rule.

But the send count matters. I haven't settled how many contacts a domain must reach before the system can make that call.

Until then, I'd review the counts before a swap. A few unanswered emails shouldn't trigger a purchase.

The campaign also needs to be worth keeping alive.

My benchmark for a healthy campaign is more than 1 positive reply per 500 contacts - a positive reply, not a booked meeting.

If the whole campaign is failing, rethink who you're targeting, the offer and the message. Don't just give it more domains.

Keep one record per domain

To make those decisions, keep one record per domain with:

• Campaign context - audience, script version and seven-day comparison window
• Inventory status - purchase date, preparation history, assigned owner and reserve readiness
• Response data - sends, contacts, human replies and positive replies
• Delivery problems - bounces, provider errors, complaints and account restrictions

Did the drop follow a change to the campaign? Or is it mostly a few domains? These records help you check.

I'd check that the accounts are set up to prove who sent the email. I'd also check for sending limits before buying anything else.

Keep spare capacity ready. Use the results to decide whether to swap domains or change the campaign.

Hold double the usable capacity

Hold double the usable sending capacity. Half is for the active campaign. The other half is ready in reserve.

Purchased domains that still need inboxes or preparation don't count as ready reserve.

For my Azure setup, I use up to 100 inboxes per domain. Each sends up to 5 cold emails per day.

100 inboxes x 5 daily sends = 500 configured daily sends per domain.

That's my setup, not a Microsoft quota. It doesn't mean every domain can safely send that much.

If you're using 2,000 daily sends of capacity, hold 2,000 active + 2,000 ready reserve = 4,000 total daily capacity. The reserve is there to replace capacity when needed, not to double your current sending volume.

I'd size the reserve against usable capacity, not just match the number of domains on a spreadsheet.

When a domain meets the rules for a swap, use a ready domain from reserve. Then have the system buy and prepare more, within a spending cap.

Set that cap before you turn on purchases. Don't take the old domain out until the new one is ready.

Prepare inventory before the campaign needs it

Stagger purchases across vendors rather than wait until the reserve is empty.

I'd choose general-purpose domains that fit the client's market. Make it clear which company is sending the email.

In our process, we wait 2 weeks before inbox setup. The inboxes then need more time to prepare before we use them.

That delay is part of our process, not a provider requirement.

Aged domains and prewarmed inboxes are worth a look for Azure. I'd also look at them when buyers use email security gateways to screen their mail.

Check what an older domain was used for before you buy it. With prepared inboxes, ask to see their sending history.

I've discussed 90 days of preparation for those buyers. But day 90 isn't a reason to jump straight to full volume.

I'd increase volume based on what those accounts have actually been sending and how they're performing.

Review what the campaign repeats

Alongside the infrastructure, use at least 20 subject lines per campaign and write new scripts weekly.

The variations should come from the offer and audience segment, not just rearrange the opening sentence.

Use plenty of signature variants too. Have a different, real sender every 10-20 inboxes. Make it clear who they are.

If you can't support that with real sender identities, don't fill the remaining accounts with fictional people.

The company being represented should remain clear too.

These are variables I'd manage in the setup, not a promise that providers can't connect the accounts.

EmailGuard's domain masking shows your site under the sending domain. It uses a reverse proxy, which fetches the site for the visitor. You can choose a shared or dedicated internet address, with a secure connection.

If the website host doesn't support the proxy, it may fall back to a redirect and lose the mask.

I wouldn't treat that as a guarantee of bot blocking or complete reputation isolation for the main domain.

Before you add another ready domain, read the last seven days of replies. Separate positive replies from the rest.

More on the campaign itself

For more on what to write and who to contact, browse the free videos on my YouTube channel.

- Mitch

P.S. Something I've been thinking about: The greatest builders seem to find a space where everyone else's experience counts for less. Emerging industries give young founders that opening. Nobody has been doing it for 20 years, so energy and creativity can take you a long way. You get to try things while everyone else is still arguing about how things are supposed to work. It makes me think of Conor McGregor coming into the UFC (Ultimate Fighting Championship). He had experience, obviously, but he wasn't waiting his turn. He brought his own style and made people pay attention.