Sender reputation best practices for marketing agencies

Agencies send on behalf of many client domains and must isolate reputation per client.

What sender reputation is#

Sender reputation is the score mailbox providers assign to a sending domain and IP based on complaint rates, bounce rates, engagement, spam-trap hits, and authentication history. It determines whether mail is delivered, filtered, or rejected.

Why it matters#

Reputation is the dominant factor in inbox placement. Content matters far less than the trust a provider has in your domain.

Implementation plan for marketing agencies#

1. Register in Google Postmaster Tools and Microsoft SNDS to see your domain and IP reputation directly.
2. Keep spam complaints below 0.1% (Gmail's threshold is 0.3% for enforcement) and hard bounces below 2%.
3. Segment by engagement and stop sending to contacts inactive for 90+ days.
4. Authenticate with SPF, DKIM, and DMARC so reputation accrues to your domain rather than a shared IP.
5. Ramp volume gradually after any pause longer than two weeks.

Priorities specific to marketing agencies#

Agencies send on behalf of many client domains and must isolate reputation per client. Weight your effort toward the steps above that address this constraint first, and measure with metrics that match how marketing agencies generate value from email.

Common mistakes#

• Buying or scraping lists, which seed spam traps into your database.
• Blasting an entire list after months of silence.
• Ignoring Postmaster Tools until placement has already collapsed.

Frequently asked questions#