What it is built from
Every large receiver maintains an internal score for your sending domain and your sending IP. It is assembled from engagement — opens, replies, deletes without reading, moves out of spam — and from complaints, bounce rate, spam trap hits, sending volume consistency, and how long you have been sending at all.
None of it is published. There is no dashboard, no number, and no appeal. You infer it from where your mail lands.
Domain versus IP
Both exist and they behave differently. IP reputation matters most when you own dedicated IPs; on shared infrastructure like Google Workspace you are inheriting a pool reputation you do not control. Domain reputation is yours alone and follows the domain wherever it sends.
For cold email, domain reputation is the one you are managing. It is also why burned domains get replaced rather than repaired — the reputation is attached to the domain and does not wash off.
How it gets destroyed
Sending volume that spikes rather than ramps. New domains sending at full rate on day one. High bounce rates from unvalidated lists. Consistent non-engagement, which for cold email means bad targeting. Volume that outruns what the fleet was warmed for.
Almost every one of those is a capacity or hygiene failure rather than a technical one, which is why authentication alone does not save a badly run campaign.
Check yours
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Common questions
How long does it take to build?
Weeks, not days. Warmup establishes a baseline over two to four weeks; genuine reputation accrues over months of consistent sending.
Can I check my reputation directly?
Not really. Google Postmaster Tools gives you a view for Gmail if you have enough volume. Otherwise you infer it from placement testing and from where replies actually come from.
Does a new domain start with bad reputation?
It starts with none, which is not the same thing but behaves cautiously at first. That neutral state is exactly what warmup is for — establishing a pattern before volume arrives.
Related concepts
Everything above is diagnosis. To confirm a fix worked you need placement data — seed accounts across the major providers, plus the DMARC aggregate reports read as a trend rather than a wall of XML. GlockApps is what I run for both.
See GlockApps →Affiliate link — it costs you nothing and help keep these tools free. Everything I use →If this is the thing going wrong
The pages explain it. If you would rather it was simply fixed, that is the work I do.