Upgrading to 32GB RAM for Mac mini Server (MD389LL/A)
No. That Mac mini is limited to 16 GB max ram. 

You can be pretty sure that if it's not mentioned in Everymac or sold by OWC[MacSales] or ramjet.com, it can't be done. These reputable sellers will always provide good research and advice if more memory can be used past Apple official specifications. 

Whether you would choose them as your vendor or not, they tend to cover all possibilities &amp; often support things that Apple never intended.