Reactivation campaigns: how to mail dormant users without a block

A reactivation campaign inverts everything that makes mail deliverable. You are sending to the least engaged people on your list, many of whose addresses no longer exist, at the largest volume you have attempted in months, from a domain whose recent sending history is thin. That combination produces bounces, complaints and spam-trap hits simultaneously, which is the exact signature of abuse. The campaign can work, but only if it is sequenced.

Before any of it: validate and segment

1. Remove the dead. Run the list through verification and drop anything invalid, role-based (info@, sales@, admin@) or syntactically broken. Hard bounces are the fastest way to a block, and a two-year-old list can bounce at double figures.
2. Segment by recency of engagement, not by signup date. Last 90 days, 90–180, 180–365, over a year, never engaged.
3. Decide where to stop. The "never engaged" and "over two years" segments are usually not worth the risk at all. Recycled spam traps — addresses that were real, went dormant, and were turned into traps — live exactly there.
4. Check consent. If you cannot evidence that these people opted in, the campaign is a compliance problem before it is a deliverability one.

Then ramp, in this order

Working from engaged outward means your early sends generate positive signals that offset the weaker ones later, and it means your first bad day happens at low volume with a smaller segment to blame.

Stop conditions, decided in advance

Write these down before the send so nobody has to make a judgement call under pressure.

• Hard bounces above 2% on any batch: stop, re-verify, do not continue.
• Complaint rate approaching 0.1%: stop increasing. Google's published threshold for bulk senders is 0.3% and you do not want to find out how close you can get.
• Any 550 5.7.1 naming a blocklist: stop everything and investigate the source.
• Per-provider placement dropping 15 points week on week: hold volume, do not reduce to zero.

A campaign with no stop condition always runs to the end, which is how a win-back becomes a quarter of remediation.

Make the message easy to leave

Counter-intuitively, the most protective thing in a reactivation email is a prominent, honest unsubscribe — and, for bulk mail, one-click unsubscribe headers, which Gmail requires of bulk senders. People who do not want your mail will either unsubscribe or report it as spam, and the difference between those two outcomes is how easy you made the first one. A single-question "do you still want to hear from us" with a clear opt-out outperforms a disguised re-engagement sequence, because it converts complaints into clean suppressions.

Send from a domain or subdomain that is not carrying your transactional mail. If the campaign goes badly, password resets and receipts should be unaffected.

What not to do

Do not warm a domain specifically to survive one big reactivation send and then push the whole list through it; the ramp is undone by a single spike. Do not send to an unverified list because verification costs money — a block costs more. Do not re-mail non-openers of the reactivation email: they have told you. Do not buy engagement to make the campaign's numbers look survivable; pools of controlled mailboxes manufacturing opens, clicks and replies are what Validity's Heatwave blocklist, launched 3 September 2026, exists to catch, and because it lists domains rather than IPs and publishes no thresholds, no tool — ours included — can offer you exemption from it. And do not judge the ramp by a reputation grade: Google Postmaster Tools retired its domain and IP reputation charts, so your evidence is Gmail spam rate plus per-provider seed placement.

If it goes wrong

Stop sending entirely rather than tapering. Identify whether the trigger was bounces, complaints or a trap hit — the first two are in your own data, the third usually shows up as a sudden block with no warning. Suppress the segment involved permanently. Resume at low volume to the 90-day segment only, for two weeks, and watch placement before touching anything older. If a blocklist entry appeared, use that list's free review path only after the sending is actually fixed; a rejected request makes the next one slower.

MailPilot helps with the before and during: it warms mailboxes over OAuth or SMTP/IMAP, checks SPF, DKIM and DMARC on the sending domain, measures real per-provider inbox placement so a reactivation batch's effect is visible within a day, and tracks per-mailbox reputation daily so you can see which mailbox absorbed the damage.