Only one different recipient for correspondence type &1 is possible

What causes this issue?

You have tried to define two different correspondence recipients for
correspondence type &V1&.
This is not permitted.

System Response

The different correspondence recipients are not saved.

How to fix this error?

Change your entries such that a maximum of just one different
correspondence recipient is defined for each correspondence type.
Carry out the action again.

Procedure for System Administrators

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.