You want an easy way to forward all mails for one or more user(s) to another user? There are several ways to achieve this. One of them is to run the following command in powershell after you connect to Office 365.
Set-Mailbox user1 -ForwardingSmtpAddress email@example.com -DeliverToMailboxAndForward $false
In this case, user1 is the mailbox you wish to forward mail for, and firstname.lastname@example.org is the address that you would like to forward the email to. Because we set DeliverToMailboxAndForward to false, a copy of the email will NOT be kept in the Office 365 mailbox.
Do you want to turn off the forwarding?
Set-Mailbox user1 -ForwardingSmtpAddress $null
If you want to check ForwardingSmtpAddress just issue the following command:
Get-Mailbox -Identity user1 | fl DeliverToMailboxAndForward,ForwardingAddress,ForwardingSmtpAddress
Note: if you don't know how to connect to Office 365 from powershell please read this post.