Sender reputation: what it is and how to protect it

How it works

Mailbox providers keep score. Gmail tracks volume, feedback and limits per domain and per IP address, and shows both reputations in Postmaster Tools.

• Domain reputation follows your sending domain, whichever provider sends for it.
• IP reputation belongs to the servers that deliver the mail. On a shared IP, every sender using it affects it.

What moves it: spam complaints, mail to people who never signed up, missing authentication, bursts and sudden jumps in volume, and mail that bounces or gets deferred. Google's advice is the reverse of that list: send only to people who asked, authenticate, and send at a steady rate.

Why it matters

• It decides where mail lands. Good reputation means the inbox. Poor reputation means the spam folder, throttling or rejection.
• It's slow to repair. Gmail notes that improvements in spam rate take time to show in how your mail is classified.
• It travels with your domain. Changing provider doesn't reset a damaged domain.

How Mimeo handles it

Mimeo isn't the sender: your own Postmark or Resend account delivers, and the reputation belongs to your domain and your provider (Sending providers). Mimeo's part is to keep what it sends from damaging it:

• Bad addresses stop at once. Hard bounces and complaints suppress the person as soon as your provider's webhook arrives.
• Big sends are paced. Every broadcast drains at a set rate per hour, most engaged people first, and can be canceled mid-send if bounces climb (sending pace).
• Cold lists are never mailed all at once. An inactivity flow lets quiet people in a daily batch at a time.
• Links match the sender. Tracking and unsubscribe links ride your own sending domain, so the From address and the links agree (why it matters).

Watch the reputation itself in your provider's dashboard and in Postmaster Tools. See Mimeo terms for Mimeo's sending words.