Based on virtualization requirements for Exchange 2013 on Microsoft TechNet which was update in May 2015, deployment on Microsoft Azure virtual machines is supported if all storage volumes used for Exchange databases and database transaction logs (including transport databases) are configured for Azure Premium Storage.

Exchange 2013 Iaas is supported if all supportability requirements are met.

For more information about Exchange 2013 virtualization requirements, check the below post from Microsoft TechNet:

https://technet.microsoft.com/en-us/library/jj619301(v=exchg.150).aspx

Abdul Jalil Abou Alzahab