To increase the send and receive limit for all users on Exchange there are 3 settings that need adjusting. Global Transport, Receive Connector, Send Connector.

Global Transport Settings

To check current configuration:
Get-TransportConfig | ft MaxSendSize, MaxReceiveSize

To set a new limit:
Set-TransportConfig –MaxSendSize 30MB –MaxReceiveSize 30MB

Receive Connector Settings

To check current configuration:
Get-ReceiveConnector | ft name, MaxMessageSize

To set a new limit:
Set-ReceiveConnector “Windows SBS Internet Receive Servername” –MaxMessageSize 30MB

Send Connector Settings

To check current configuration:
Get-SendConnector | ft name, MaxMessageSize

To set a new limit:
Set-SendConnector “Windows SBS Internet Send Servername” –MaxMessageSize 30MB

Source: Official SBS Blog

You may receive Event 24 (Expired Certificate) or Event 25 (Certificate Expiring Soon) errors after using the “Add Trusted Certificate Wizard” to install a new Certificate.

The following steps can be used in Exchange Management Shell to manually remove the old certificate.

Get-ExchangeCertificate |FL

Remove-ExchangeCertificate -Thumbprint ‘OldCertificateThumbprint’

Source – Technet

Symptoms:
1. Outlook Web Access shows: A problem occurred while you were trying to use your mailbox.
2. Outlook won’t connect to exchange.

Mailbox may be quarantined.

Removing mailbox from quarantine
1. Delete REG KEY on server:
HKLM\SYSTEM\CCS\Services\MSexchangeIS\Servername\Private-dbguid\Quarantined Mailboxes\ {Mailbox guid}.

2. Restart Microsoft Exchange Information Store Service

Source – Technet Blog