qwertzguy is right, but you may need more information.
Your issue stems from the default gateway being set when connecting to the two networks. The default gateway is what telss your computer how it gets to any IP network it is not directly connected to.
When you connect to your work network, and do
ipconfig in a cmd prompt, you'll see default gateway set. When you connect to the android phone, you'll have another default gateway set, which is probably getting priority over the first. In
ipconfig you'll see that you have an ip address and a network mask. For any IP address that does not fall within this network your computer will attempt to connect to it via the default gateway. Your email and file servers at work are very likely not on the same network as you, and so will be access via the default gateway. As your android phone sets a default gateway it will attempt to connect to them via your phone. This will clearly not work.
In order to use the
route command, you need to know the ip address ranges that your work uses, and ensure they are routed to the gateway that your work connection sets. Given that they most likely use private address ranges, the following routes will probably cover all scenarios:
route add 10.0.0.0 mask 255.0.0.0 <work gateway IP>
route add 192.168.0.0 mask 255.255.0.0 <work gateway IP>
route add 172.16.0.0 mask 255.240.0.0 <work gateway IP>