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Marketing Agencies

How to Audit an Email Marketing List Before Sending on Behalf of a Client

Agencies that send to unaudited client email lists risk deliverability damage that outlasts the campaign. Here's the audit process to run before every client send.

Key Takeaways
  • A bad client list damages the client's sending domain — which damages every future campaign you run for them
  • Always request the raw CSV before it's uploaded to the ESP — review before you send
  • Check for typo domains, duplicates, role addresses, and suppression list alignment
  • Lists not emailed in 6+ months should be verified with a paid service before sending
  • Document every audit — this protects the agency if deliverability problems are blamed on list quality

The Agency Risk That Most Don't Think About

When an agency sends a campaign from a client's sending domain, the agency's reputation is tied to the client's email list quality. A high bounce rate damages the client's sender reputation — which damages every future campaign the agency runs for them.

Protecting the client's list health is part of the service.

Why Client Email Lists Are Often Dirty

Clients collect emails through many channels with varying data quality standards:

  • Event registrations with typos
  • Webinar signups from years ago that were never cleaned
  • Trade show badge scans that capture business cards indiscriminately
  • Purchased lists (which should be an immediate red flag)
  • CRM exports that include unsubscribes not synced to the ESP

Sohovi finds gaps, duplicates, and format errors in your CRM data — so your team is working from records they can trust.

By the time a list reaches an agency for a campaign send, it may have significant problems the client doesn't know about.

The Agency Pre-Send Audit Protocol

Step 1: Request the list in CSV format

Never send from a list you haven't reviewed. Ask for the raw CSV before it's uploaded to the ESP.

Step 2: Check list metadata

How many records? What's the oldest opt-in date? What's the source of each segment? Ask the client these questions — they reveal list quality quickly.

Step 3: Run basic format checks

Sohovi lets you set up validation rules for any column and instantly see which rows fall outside them — no code or SQL required.

  • Every record has an email address (no blanks)
  • All emails follow the basic pattern (something@something.something)
  • No obvious typo domains (gmial, yhaoo, hotmal)
  • No role addresses (info@, admin@) if this is a promotional send

Step 4: Deduplication

Sort by email address. Remove duplicates. A customer on the list twice will receive the email twice — generating potential double unsubscribes and spam complaints.

Sohovi automatically finds every duplicate in your dataset — including near-matches — and shows you exactly which rows are affected.

Step 5: Suppression check

Confirm the list has been suppressed against:

  • Previous hard bounces
  • Previous unsubscribes
  • Any suppression lists the client maintains (competitors, employees)

Step 6: Verification for lists not recently sent

For any list or segment that hasn't been emailed in 6+ months, run it through an email verification service before sending. The cost ($10–50 for most lists) is trivial compared to the deliverability damage from a high bounce rate.

Documenting the Audit

Keep a record of every audit: list size, issues found, actions taken, final clean list size. This documentation protects the agency if a deliverability problem is later blamed on "the list the agency used."

Frequently Asked Questions

What bounce rate should trigger concern before a send?

If verification predicts more than 3% invalid addresses, do not send without cleaning. Most ESPs will flag accounts with bounce rates above 2%, and some will suspend sending privileges.

What if the client insists on sending to an unverified list?

Document your recommendation and their decision in writing. If they insist on proceeding, ensure they understand the deliverability risk. Consider including a list quality clause in your agency contract.

How do I handle a purchased list a client wants to use?

Decline, or be very clear about the risks. Purchased lists have no opt-in, are often recycled and full of spam traps, and violate the terms of service of most ESPs. A single spam trap hit can result in account suspension.

Selva Santosh

Data quality, for people who ship

Selva writes practical guides on data quality, profiling, and governance to help teams ship better data.

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