Sending marketing emails to unengaged or undeliverable contacts — sometimes called "gray matter" — actively damages sender reputation and email deliverability. It skews open rates, increases bounce rates, and can push senders into higher HubSpot subscription tiers unnecessarily. A periodic database hygiene run is the primary remedy.
This article documents the recommended process for cleaning a contact database, reducing marketing contact counts, and improving deliverability, drawn from a 2026-03-19 HubSpot setup session with Citrus America.
Two compounding issues arise when contact databases are left unchecked:
"They're referring to that as gray matter, and it actually hurts us." — Melissa Cusumano, 2026-03-19 meeting
Run these steps in sequence. Each stage gates the next.
Export all contacts with email addresses and run them through a bulk list hygiene tool. Identify addresses that are undeliverable (hard bounces, invalid domains, role addresses that reject mail, etc.).
Action: Delete the email address field for any undeliverable contact — do not delete the contact record itself. This prevents accidental future sends while preserving any associated history, company linkage, or deal data.
Compile a separate list of contacts who now have no email address on file. This becomes the input for the enrichment step.
Export the full contact list (anonymized — no client name or branding needed in the prompt) and submit to an AI tool for analysis. Ask it to assess:
This produces a rough segmentation without manual review of thousands of records.
"We just say, here's a spreadsheet, tell us about these people. It's just a list of people." — Mark Hope, 2026-03-19 meeting
Confidentiality note: Pass only the contact data itself — no client identifiers. The AI has no context about whose list it is.
For contacts that the AI flags as potentially valuable but incomplete (missing phone, LinkedIn, correct email), run enrichment via a tool such as Hunter. This is only cost-effective for contacts that show some signal of relevance — don't enrich the full list.
Enrichment targets:
- Contacts with no email (from step 1) who appear to be real prospects
- Contacts with engagement history but missing contact fields
Produce a segmented output for client review:
| Segment | Description | Recommended Action |
|---|---|---|
| High-priority | Engaged, complete data, relevant industry | Keep as marketing contacts |
| Enrichable | Incomplete data but promising | Enrich, then reassess |
| Unengaged | Never opened, never clicked, no deal history | Convert to non-marketing or delete |
| No email / undeliverable | Email removed in step 1 | Enrich or delete |
Present this to the client for final disposition decisions. The client confirms which segments to delete, convert to non-marketing, or retain.
HubSpot charges only for marketing contacts. Contacts can exist in HubSpot as non-marketing contacts at no additional cost — they remain in the CRM, retain their history, and can be associated with deals and companies, but cannot receive HubSpot marketing emails.
For contacts that are not ready for active marketing but shouldn't be deleted (e.g., past trade show leads with no engagement), converting to non-marketing is the right call. They stay in the system without inflating the subscription.
For large prospecting lists that don't warrant HubSpot marketing contact status, bulk emails can be sent externally via AWS SES and connected back to HubSpot via API. This approach:
This is appropriate for large, lower-confidence lists where the cost of HubSpot marketing contact status isn't justified. See [1] for setup details.
As an immediate deliverability improvement — independent of a full hygiene run — switch recurring newsletters to send only to an engaged contacts segment rather than all marketing contacts. HubSpot's engaged segment typically filters for contacts who have opened or clicked within a defined window (e.g., 90 or 180 days).
Sending to unengaged contacts on every newsletter send compounds deliverability damage over time. The engaged-only approach protects sender reputation while the broader cleanup is underway.
These figures are illustrative. The actual reduction depends on engagement history and how aggressively unengaged contacts are converted or deleted.