This tutorial will allow you to increase your mailbox size limit at the domain level
After upgrading or updating your version of Parallels Plesk Control Panel, you may encounter issues where you receive the following email error – Incorrect limit value was specified. You may also encounter issues where your domain email account default size is hard-coded to 0kb. To resolve this issue and set you domain mail to an unlimited or other specified value, follow the steps below.
1. Log onto your Plesk Control Panel
2. Ensure you are in the Service Provider View ( if you are not in the service provider view, click the Interface Management link, select Service Provider View and click [OK].
3. Click the subscriptions link under the Hosting Services menu located on the left.
4. Click the desired Domain — a page will appear with options available to customize your domain.
5. Click the [Customize] menu button – The Customizing Subscription “Domain” page is displayed
6. Click On the Resources tab locate the Define limits on usage of resources provided with the subscription section of the page
7. Locate the Mailbox size input field and select the Unlimited check-box or increase the default value to your desired value ( Make sure the Mailbox input field is NOT blank )
8. Click [OK]
Congratulations – you have just increased your default mailbox size. No more errors!