I'm having trouble finding out how to do this, with Exchange Online, Office 365 and Exchange 2013 installed on our own server, the answers I've seen are confusing since one answer or feature isn't included in all.
We have email hosted on an IMAP server, which I will call this external.com. I have put together a server with Exchange 2013, it is setup for domain internal.com. The reason I did this is because our company has grown to the point that our internet is being taxed by the amount of IMAP information and we don't currently have a better option due to our location. I want people to still use their blackberries and external web and outlook from home email on external.com IMAP server. All mail goes touser@external.com, and I have set external.com to forward all mail touser@internal.com. This part is working great, the problem is internally. I need to be able to set everyone's Outlook 2010 exchange account so that it always sends asuser@external.com. I've tried doing this by powershell "Set-Mailbox user -EmailAddresses user@external.com -EmailAddressPolicyEnabled $false", which works for sending email to someone outside of the company. The issue is if dave@external.com sends an email to gord@external.com, the message just goes from dave's mailbox to gord's mailbox on the exchange server, and never goes to the external IMAP server. This means it never reaches the blackberry or external host. Is there a way of doing this without having to switch to office365 or exchange online?