Deliverability is whether your email reaches the inbox at all — and it’s decided before anyone reads a word you wrote. Mailbox providers score every sender on domain reputation, volume patterns, bounce rates, and complaint rates. Get those wrong and even a brilliant reactivation campaign talks to the spam folder. Here are the fundamentals every service business should understand before emailing an old database.

The four numbers that decide your fate

• Bounce rate — keep it under 2%. A bounce means the address doesn’t exist or rejected you. Old databases are full of dead addresses, which is why list verification before sending is non-negotiable. High bounces tell Gmail and Outlook “this sender mails junk data.”
• Complaint rate — keep it under 0.1%. That’s one spam report per thousand emails. It sounds brutal because it is: complaints are the strongest negative signal a mailbox provider has. Honest subject lines, relevant segmentation, and an easy opt-out keep this low.
• Volume pattern. A domain that sent nothing yesterday and 10,000 emails today looks exactly like a spammer. Reputation is built by ramping.
• Engagement. Replies and forwards are gold; deletes-without-reading and ignores slowly sink you. This is another reason reactivating known contacts outperforms cold lists — recognized senders get engaged with.

What “warming up” a domain actually means

Warm-up is the practice of starting a new sending domain at very low volume and increasing gradually — typically over about 21 days — so mailbox providers can build a positive history for it. Day one might be a handful of emails; by week three, meaningful volume. Skipping warm-up is the #1 way reactivation campaigns die on arrival.

Why a separate domain at all? Because your primary domain — the one your invoices, proposals, and client emails come from — is a business-critical asset. A responsible provider sends campaigns from isolated, warmed sending domains, so that even in a worst-case scenario, your main domain’s reputation is never touched. This is standard practice at Aldezard and something you should demand from any vendor. (See the full protocol in How We Work.)

Why open rates lie to you

Here’s the uncomfortable one: the open rate on your dashboard is substantially fiction. Apple’s Mail Privacy Protection pre-loads email content for its users — registering an “open” whether or not a human ever looked. Apple Mail accounts for the majority of email opens tracked (over half in most industry analyses), and MPP inflates reported open rates by roughly 25–35%.

So a “48% open rate” tells you very little. What actually correlates with revenue:

• Reply rate — a human decided to engage.
• Click-through rate — a human took an action.
• Meetings booked — the metric the business actually feels.
• Opt-out and complaint rates — the health warnings.

If a vendor reports success in open rates, ask harder questions.

A pre-send checklist for old databases

Before any reactivation campaign touches your data:

• List verified; hard bounces and role addresses removed
• Known opt-outs suppressed (you keep those records, right?)
• Separate, warmed sending domain — primary domain untouched
• SPF, DKIM, and DMARC configured on the sending domain
• Volume ramp plan (not a day-one blast)
• Honest subject lines, physical address, one-click opt-out in every email
• A human ready to answer replies fast

Miss two or more of these and you’re gambling with an asset — your data and your reputation — that took years to build.

Frequently asked questions

Why do my emails go to spam even though I’m not a spammer?

Usually some mix of: unverified old lists (bounces), no warm-up (volume spike), missing authentication (SPF/DKIM/DMARC), or content sent to unsegmented, unengaged contacts. Providers judge behavior, not intent.

How long does domain warm-up take?

Around three weeks of gradually increasing volume is the common standard. It can’t responsibly be rushed — which is why a real reactivation pilot’s first week is setup, not sending.

Should I buy an email verification tool or is that the vendor’s job?

If a vendor doesn’t verify your list before sending, find another vendor. At Aldezard, database review and verification is step one of every engagement — we won’t send to an unverified list.

Is a 40%+ open rate good?

It’s reported, not necessarily real — privacy features inflate opens significantly. Judge campaigns on replies, clicks, and booked meetings instead.

Want your old database handled the careful way? See how Lead Activation works or book a 15-minute call.