MailRoundupHandling Bounces And Complaints Without Wrecking Your Reputation
Every provider looks at how you react to negative signals more than the signals themselves. Here is the short list of behaviors that keep transactional mail landing.
Read The SMTP Reply, Not The Summary
SMTP replies are structured. The first digit tells you category:2xx is success, 4xx is a temporary failure (defer and retry), 5xx is permanent (do not retry). The three-digit enhanced status code (RFC 3463) is more specific: 5.1.1 is “mailbox does not exist,” 5.7.1 is “delivery not authorized, message refused.” A pipe that treats every failure the same is telling mailbox providers you are not paying attention.
Hard Bounces
- A permanent failure. The mailbox is invalid, the domain does not resolve, or the receiver has explicitly refused you.
- Rule: suppress the recipient immediately. Never send to that address again unless you have a verified reason (user re-entered it, for example) to unsuppress.
- Continuing to hit a hard bounce is one of the fastest ways to look like a spam operation.
Soft Bounces
- A temporary failure: mailbox full, greylisting, DNS blip, or a receiver-side rate limit.
- Rule: retry with exponential backoff for a bounded window (24 to 72 hours). After that, treat as a hard bounce and suppress. Do not retry forever.
- A pattern of soft bounces for the same recipient across many days almost always means the mailbox is gone.
Spam Complaints And Feedback Loops
When a user clicks “report spam,” participating mailbox providers send you a Feedback Loop (FBL) report. Most providers (Yahoo, AOL, Comcast, Microsoft) run FBLs; Google does not, and exposes spam rate through Postmaster Tools instead.
- Suppress on complaint, always. Even for transactional. If a user complained about a receipt, something is wrong upstream (they did not remember buying, they think it is phishing) and continuing to mail them makes it worse.
- Target complaint rate: under 0.1 percent per Google's guidance, and stay well below the 0.3 percent hard cap.
- Investigate patterns. A jump in complaints usually maps to a specific template or a specific customer. Find it before the receiver's reputation model does.
Suppression As A First Class Concept
Every mature transactional pipe treats the suppression list as load-bearing. It is not a cleanup task; it is the guardrail that keeps your reputation intact when a legitimate app bug tries to send to the same dead address a million times. On MailRoundup, suppression is applied at the API boundary: a message to a suppressed address is refused with a clear error, never silently consumed.
Send transactional email that lands.
MailRoundup is a transactional-only pipe for receipts, confirmations, password resets, and alerts. One endpoint, honest logs, no marketing traffic in the way.