Sender reputation

Sender reputation is the score a mailbox provider keeps on you. It has no public number, no API, and no appeal, and it decides whether your mail reaches the inbox, the spam folder, or nothing at all.

It attaches to two things at once: the sending IP address, and your domain. Domain reputation is the one you carry with you. Changing providers gives you new IPs and does nothing at all for a domain you have spent a year teaching Gmail to distrust.

What raises it and what wrecks it

Providers do not publish their weightings, but the direction of each signal is not in doubt.

• Complaints are the worst single signal. A rate above roughly 0.1% — one in a thousand — is treated as a problem by most providers, and the threshold where filtering begins is lower than the threshold where anyone tells you.
• Hard bounces at volume say you are mailing a list you have not maintained.
• Spam-trap hits are catastrophic, and they are the reason a purchased list is never worth it: a recycled trap is an address that was real, was abandoned, and is now watched.
• Engagement helps. Opens, clicks and replies are positive signals; a large audience that never engages is a negative one even with no complaints at all.
• Volume consistency helps. See IP warm-up.

In Sendly

Sending is on shared, actively monitored infrastructure with per-project limits, which means one sender's mistake is contained rather than borne by everyone. It also means the protective limits are real: a sudden order-of-magnitude jump in volume from a new project is exactly the shape those limits exist to catch. If you are about to migrate real volume, say so first.

Sendly does not offer a self-serve dedicated IP with a warm-up schedule you control today.