What data do deliverability consultants look for in inbox diagnostics?
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A deliverability consultant's first hour is mostly a data gathering exercise. They're pulling from four or five sources at once and looking for the one that doesn't match the others. Here's what goes on the table, where to get it, and what actually matters most.
Authentication (5 minutes to check, highest priority)
Any decent consultant starts with SPF, DKIM, and DMARC records for your sending domain. They want to see alignment (the From domain matches the SPF/DKIM signing domain), a published DMARC policy, and aggregate reports coming in. If any of these are broken, nothing else you show them matters until they're fixed.
Provider-side reputation (free, but you have to have set it up)
They'll ask for access to Google Postmaster Tools and Microsoft SNDS. These show your domain and IP reputation, spam rate, and authentication success as the providers see it. Most senders haven't set these up, which is the first homework item.
ESP engagement data
Open rates, click rates, complaint rates, unsubscribe rates, and bounce rates, segmented by campaign type and by recipient domain. The goal is to spot whether the problem is one domain (Gmail specifically getting worse) or universal. Most ESPs (Mailchimp, HubSpot, SendGrid) expose this in reports. Complaint rate over 0.3% is the red line.
List quality
Acquisition sources, recency of signup, confirmation method, and how often the list gets cleaned. A hidden scraped list or an old purchased list will show up here as bounce rate and complaint rate spikes. See list hygiene basics for what clean looks like.
Content and infrastructure
Sample emails, template HTML, the links they contain (are any shortener domains blocklisted?), the sending IP setup (shared or dedicated, warmed or cold). This is usually a fast scan unless something jumps out.
What to prioritize
If you're gathering this yourself before bringing in a consultant, do it in this order: authentication records, Google Postmaster Tools, complaint rate trend, bounce rate trend, top 2-3 recipient-domain breakdowns. That's about 80% of the diagnosis in 80% less time. When you want someone to read it with you, the SOS hotline is the fastest way in.
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