A syntactically valid address can belong to someone who never asked for a campaign. A working mailbox can also belong to a person who has already unsubscribed. Deliverability work therefore needs evidence about why each recipient is included, not merely whether a message can be addressed to them.
Record permission and expectations
Keep the collection source, date, relevant notice or choice and the intended mail purpose. These records support an operational review; they do not replace legal advice about the laws applicable to the sender and recipient. Separate permission for one purpose from an assumption of permission for every later campaign.
Google advises senders not to purchase email addresses and to send subscription messages to people who want them. Its guidance also emphasizes unsubscribe behavior and avoiding unwanted messages. Those are provider practices, not a universal legal test. Google sender guidelines.
Keep suppression stronger than imports
Define how unsubscribes, verified complaints and other exclusions reach every relevant sending system. A fresh CRM import must not silently restore an address already suppressed for that stream. Scope suppressions carefully so the organization can distinguish marketing preferences from genuinely necessary operational communication under its approved policies.
Assign ownership of conflicts. An import job should report that a record was excluded and why, without exposing private subscription history to unnecessary users. Do not solve a conflict by deleting the suppression evidence.
Read complaints with their coverage
A complaint count reflects the reports available to the sender, not all recipient dissatisfaction. Different providers and report pipelines have different coverage. Keep the source, period and denominator attached to any rate, and do not equate an internal complaint ratio with a provider dashboard metric.
Investigate campaign frequency, acquisition source and recognizable sender identity when complaints change. Authentication failures deserve their own review, but passing authentication does not establish wanted mail.
Trace an unsubscribe through a repeated import
Suppose a hypothetical newsletter contact unsubscribes in the sending platform while the CRM still exports an older eligible flag. The next import includes that contact twice. Under a declared suppression-first policy, neither duplicate should restore newsletter eligibility; a separate contact with no collection-purpose evidence remains held for review. These are expected outcomes, not observed software results or legal determinations.
An authorized test should retain the unsubscribe time, propagation time, import revision and pre-submission eligibility decision in each applicable system. If the CRM view is stale but the final send gate correctly blocks the contact, record both facts: the display issue remains, but the same evidence does not prove that unwanted mail was sent. If one sender can bypass that gate, its path needs its own repair. Complaint counts cannot substitute for verifying this control, because missing reports do not prove satisfaction.
Verify the process, not just a cleaned list
Test a controlled unsubscribe, a duplicate import and a record with missing provenance. Confirm that every affected sender applies the expected exclusion. A one-time clean-up is incomplete if the next integration recreates the problem. Close with owners, tested flows and a schedule appropriate to the actual rate of list change.
Record a defensible next step
Keep unsubscribes effective through repeat imports and every applicable sender; address validity does not establish permission. Name the owner, the evidence still missing and the condition that will close the investigation. Leave unsupported outcomes unknown.