What’s the difference between global frequency cap and per-segment cap?

Send fatigue occurs when subscribers receive so many emails they stop engaging, or worse, start complaining.

The symptoms:

Open rates declining over time
Click rates dropping while open rates stay stable (scanning but not acting)
Unsubscribe rates increasing
Complaint rates rising
Engagement concentrated in smaller portion of list

Causes beyond just volume:

Repetitive content that feels like the same message
Irrelevant emails to wrong segments
Promises not matched by value delivered
No variation in format, tone, or offer type

Prevention strategies:

Frequency caps limit how often any individual receives email.

Content variety ensures each email feels worth opening.

Engagement-based suppression reduces frequency to those showing fatigue signs.

Sunset policies stop sending to chronically unengaged contacts.

Think of subscriber attention as a finite well. Draw from it too quickly and it runs dry. Draw at sustainable rates and it replenishes. Every email either fills or depletes that well, send accordingly.