Why deliverability starts before you hit send

By the time you're ready to send, the list has been shaped by everything that came before — how each address got on it, whether the cleanup from the last campaign happened on time, whether the audience has stayed engaged or drifted off without anyone noticing. All of that affects how mailbox providers handle the next campaign. They respond to the list more than they respond to the email itself.

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What mailbox providers are reading

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Sender reputation gets talked about like it lives in a single score somewhere. In practice it's a set of behaviors that mailbox providers watch over time: how often complaints come in, how many addresses bounce, how engaged the recipients are, and how those numbers compare with other senders hitting the same inbox.

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Gmail's filtering is now personalized at the recipient level. The same email can land in the main inbox for one subscriber and in the promotions tab for another, based on how each person has engaged with your domain in the past. So every campaign is doing two things at once: delivering a message, and giving mailbox providers more data on whether to trust the sender next time.

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A list carrying inactive subscribers and undeliverable addresses pushes the bounce rate up as soon as the email goes out. Mailbox providers see those numbers before any opens or clicks can balance them out. 

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What inbox placement depends on

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Three pre-launch decisions tend to shape what mailbox providers see when the campaign goes out.

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Cleanup matters. Bounces, unsubscribes, complaints, and generic addresses like info@ or sales@ from the previous campaign have to come off the list before the next one goes out, not just get logged for someone to look at later. A record still on the list is a record the next campaign is going to send to.

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Audience age is another factor. Lists don't stay current. People change jobs, change providers, lose interest, and stop opening. A segment that performed well eighteen months ago can carry a meaningful portion of records that no longer have any reason to hear from the brand.

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How the list gets segmented matters too. A campaign that goes to the whole list and one that goes only to engaged subscribers will perform differently, even with the same message. Sending broadly when only part of the audience is paying attention pulls engagement down across the whole campaign, and mailbox providers use that drop to decide where the next one lands.

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What a list worth sending to looks like

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Whether a list is healthy enough to send to comes down to four things our team looks at together: accuracy, freshness, depth, and breadth.

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• Accuracy is whether the address belongs to a real person who can receive mail.
• Freshness is whether the record is still good today, not just at the moment it was collected. Someone who was shopping for a car two years ago has almost certainly bought one by now, and a list that treats them like a prospect is paying to reach someone who's moved on. 
• Depth is whether the list is large enough to support segmentation that helps engagement, instead of forcing every email to go to everyone. 
• Breadth is whether enough is known about each subscriber to decide whether this particular email belongs in their inbox today.

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When all four hold up, every campaign has a chance to build sender reputation. When even one is off, every campaign becomes a chance to damage it instead.

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This is the standard our own database is held to. Every one of the more than 200 million records in our database, carries opt-in date, opt-out dates, and sources. We evaluate the records continuously, not just when an address is first added—striving to increase accuracy, and validity.

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List management before launch

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A few practical habits separate teams that hold inbox placement over time from ones that lose it slowly.

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Cleanup comes first. Whatever the last campaign produced — hard bounces, complaints, unsubscribes — gets pulled off the list before the next one goes out, not just flagged in a column for someone to look at later.

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Inactive subscribers work against the sender. A person who hasn't opened an email in twelve months will pull engagement numbers down on the next campaign, and mailbox providers will use that drop to decide where future campaigns land. Sending to a quiet segment to keep the audience size up is a trade most teams come to regret.

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Checking the list against current data has to happen on a regular basis, not just when an address is first added. Email lists go stale between campaigns, sometimes quickly. Staying ahead of that means revisiting the list on a schedule that matches how often the audience changes.

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The same campaign shouldn't go to everyone. The list gets split by how recently each subscriber opened or clicked. The most engaged group goes first, so mailbox providers see strong numbers before weaker ones. The rest gets separate, smaller campaigns to win them back, not every campaign by default. Subscribers who haven't engaged in a year or more come off the list entirely.

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Our database runs through this process on a monthly cycle. Records get scrubbed against an internal blacklist of opt-outs, known complainers, bounces, and known bots, then sent through third-party email validation and deliverability screening. New records pass through a proprietary verification step that looks for suspicious activity associated with bots before being added to the file. By the time a client's campaign deploys against any segment of our database, this work has already happened.

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This is the same logic we apply to digital media. The quality of the audience reached determines what happens after the campaign goes out. Larger lists don't beat smaller, cleaner ones. They put more reputation at risk every time you send.

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Hitting send won't fix this

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Once a campaign goes out, the open rates, bounces, and complaints all become part of the sender's reputation, and reputation moves slowly. The damage from a bad campaign doesn't end with that campaign. It makes the next one harder, and the one after that.

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The quality of the audience reached determines what happens after the campaign goes out. Every weak record on the list makes future campaigns harder to deliver.

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What the dashboards report after the fact follows from decisions made before the campaign went out. The campaigns that hold up over a full year come from teams that treat list management as ongoing work.

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Where deliverability fits in

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We talk about email at Site Impact as part of how marketers find, get, and keep customers. Keeping customers depends on the email reaching them. By the time the email goes out, the work that determines where it lands is already done.