If for some reason you reduce the maximum message size in Exchange, be careful because your users might experience the issue below. Let’s take an example: Exchange organization is configured to allow e-mails only up to 30M B in size; Users receive e-mails over 20MB in size; Exchange organization is reconfigured to only allow e-mails only up to 20MB in size. In this scenario, users might not be able to delete the “oversized” e-mails (over 20MB) in Outlook Web App [OWA]. When using Outlook, the local copy of e-mail is deleted, but not the one in the server. Even though we can use the MessageSize parameter with the Advanced Query Syntax in Outlook, the Search-Mailbox cmdlet doesn’t support it to it is not easy for an administrator to search for these messages from Exchange. The workaround is to temporarily increase the user’s MaxSendSize and MaxReceiveSize limits and then delete the e-mail using OWA/Outlook.