Nowadays, in the era of communications, "snail mail" is not used anymore. An e-mail has many advantages. First, it can be set to be received on the client's/customer's device, such as smart telephone, so the answer could be inmediate.
A further action the sender should take is to set when the reader will receive the mail , or even when will he/she read it. On the other way round, the sender could set his/her mailbox when he/she is out of the office.
Skype is also a great way to deliver a message. You can chat, as in a normal conversation, and you can even have a video call
