What complaint threshold should I aim for as a sender?

Your goal as a sender is different from the maximum allowed by providers. An expert captain does not aim to just miss the reef; they aim for the center of the deep channel.

While providers may tolerate rates up to 0.10% (as defined in their rules), the expert benchmark is fewer than 1 complaint per 10,000 messages (0.01%).

Why? Because complaint rates are volatile. A single misjudged subject line or a poorly segmented list can cause a sudden spike. Aiming for this ultra-low 0.01% rate builds a reputational buffer, which ensures that one bad voyage doesn't get your entire fleet blocklisted.