Gmail will be perfect for that.

In his Gmail account, tell him to follow the following steps:


Sign in to Gmail.
Click Settings and select the Accounts and Import tab.
Under Send mail as, click Add another email address.
In the 'Email address' field, enter the address from which he will be sending emails (your address)
Click Next Step >> and then click Send Verification. Gmail will send a verification message to your email address to confirm that he can use it.


Then you will receive the email verification, you just have to approve it.

Warning: Be careful though, I don't think you can remove this privilege from his accounts yourself or force him to remove your email address later on.

Source

How to allow someone else to send emails in my name?
I'm working on a ERP / Accounting (lots of tables and data) web app and was wondering what color scheme would be appropriate for this type of application? Users will be sitting in front of their computers for 8+ hours enetering lots of data on daily basis and I would like to  make that experience as comfortable as possible to their eyes.

Most of these application I've seen are using some sort of a white/grey/blue scheme with white being dominant but I'm concerned that this color might strain their eyes to much especially considering different brightness of monitors and working in the dark. 

Any help would be appreciated.
