Can we use our corporate email server to SMTP relay through your servers?

In short the answer is yes however we do not support it with our standard email hosting accounts.
Some corporate customers who run a local Mail Server or Exchange Server may want to relay their outgoing SMTP email through our servers.  This can be done however if you run into difficulties we recommend that you contact your IT Department or IT support provider for assistance as it is not a supported method with our standard account types.
That being said if it is set up properly you can relay your local server's SMTP email through our servers.  You will need to enable SMTP authentication and create an email account (ie. within your Hosting Control Panel specifically for authenticating the relay.
Should you have problems set up the relay account (ie. within a standard email program and use our recommended (standard) email settings to test.  If the messages are accepted and delivered then the problem lies within the configuration of your local server and we recommend having your IT department OR IT consulting agency to troubleshoot.