Certainly, I'll make sure he gets that.

• You have been trying to speak to Mr. Jones on the phone.
• He is not at work.
• You have left a message. (Could you ask him to call me back, please?)
• The receptionist says this:
• Certainly = of course. (Yes, I will ask him.) Both expressions are fine in this sentence.
• I'll make sure he gets that = I guarantee he will receive the message.

This sentence is an example of telephones, business.