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What is email sender reputation?

Also called: domain reputation, IP reputation, email reputation

Sender reputation is how mailbox providers such as Gmail and Outlook judge the trustworthiness of your sending domain and IP addresses, based on signals like spam complaints, bounces, spam trap hits, engagement and authentication.

By John Britton, VP of Marketing, MedicalProspects · Updated November 4, 2026 · Email & Deliverability

Why it matters for healthcare sales and marketing

Reputation decides whether your emails reach the inbox or the spam folder, for every campaign you send. One careless send to an old, unverified list can hurt it for weeks.

How it works

  • Hurts it: spam complaints, hard bounces, spam trap hits, sudden volume spikes, low engagement.
  • Helps it: authenticated mail (SPF, DKIM, DMARC), verified lists, steady volume, relevant content, easy unsubscribe.
  • Monitoring: tools such as Google Postmaster Tools show how Gmail sees your domain.

Google and Yahoo now require bulk senders to authenticate their mail, offer one-click unsubscribe and keep spam complaint rates low.

Comparison of what hurts sender reputation (complaints, hard bounces, spam traps, volume spikes, low engagement) and what helps it (authentication, verified lists, steady volume, relevant content, easy unsubscribe).
Sender reputation decides inbox or spam for every future campaign.

Example

Illustrative scenario. A company launches outreach from a brand-new domain at full volume and sees most emails land in spam. It pauses, sets up authentication, warms the domain gradually with its most engaged contacts, and only then adds new verified lists.

Common mistakes

  • Blasting from a new domain. Warm up gradually.
  • Sending to old, unverified lists. Verify close to the send.
  • Making unsubscribing hard. Frustrated recipients click "spam" instead.

Related terms

  • Email Authentication (SPF, DKIM and DMARC)SPF, DKIM and DMARC are email authentication standards that prove a message really comes from your domain. SPF lists the servers allowed to send for you, DKIM adds a cryptographic signature, and DMARC tells receivers what to do when checks fail.
  • Spam TrapA spam trap is an email address used by mailbox providers and blocklist operators to catch senders with poor list practices. It belongs to no real person who signed up, so any email it receives signals that the sender's list wasn't collected or maintained properly.
  • Bounce Rate (Hard and Soft Bounces)Bounce rate is the share of sent emails that were returned as undeliverable. Hard bounces are permanent failures, such as an address that doesn't exist; soft bounces are temporary, such as a full mailbox or a server that is briefly unavailable.
  • Email VerificationEmail verification is checking that an email address is correctly formed, belongs to a domain that accepts mail, and points to a mailbox that exists, before you send to it. For healthcare lists it also means confirming the address still belongs to the right person in the right role.
  • Suppression ListA suppression list is the set of email addresses you must never send to, such as people who unsubscribed, addresses that hard-bounced and people who marked your email as spam. It should apply across every tool and campaign you send from.

Put it to work

Sources

  1. Email sender guidelines, Google
  2. Postmaster Tools, Google

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