Unable to change mailbox size in Plesk: The specified limit is invalid

Symptoms

• Unable to change mailbox size under Domains > example.com > Email Addresses > Mailbox > Another size with the following error :

  The specified limit is invalid

• Mailbox size parameter is set to Unlimited for subscription's service plan under Service Plans > service_plan_name  > Resources .

• Subscription is in Locked status:
  

Cause

The subscription is not synchronized with Service plan settings.

Resolution

1. Log into Plesk.

2. Synchronize the subscription with Service plan under Subscription > example.com > Unlock & sync .