SAP Knowledge Base Article - Public

2723259 - Server Side Synchronization fails with "ISSM-004: Foreign customization detected in user's mailbox"


End user synchronization fails with an error "ISSM-004: Foreign customization detected in user's mailbox - set by instance XYZ", where XYZ is the tenant URL.


SAP Cloud For Customer

Reproducing the Issue

  1. Login to system.
  2. Navigate to E-mail Integration work center.
  3. Navigate to user settings, you observer the error.


The issue occurs because user's mailbox was already initialized on a different tenant previously. The initial tenant URL is shown in the message. Potential case - if user with the same mailbox switches from test to production tenant.


  1. Log-on as a key user on affected tenant.
  2. Find affected user.
  3. Click Gear icon in top right-hand side and click Re-initialize User's mailbox.
  4. Start synchronization.
  5. If synchronization still works on the initial tenant - the same error will occur on that tenant.


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