You can reach Michael by mail (although it may take a while), or through e-mail using Access Corrections SecureMail. Anyone can set up an account on there. It costs a minimum of $10.00 for Shared Credits. With those he can receive texts, pictures, and also respond to you.
Letters must be sent in white envelopes. No cards, but most pictures are OK (besides nudes, drugs, or alcohol containers). His kidnappers have delicate sensibilities and will usually throw away anything that offends them. Then he will never know you wrote.