How to view emails from .mil address sent to personal (hotmail,ect.) that are encrypted

[Mahesh Cherian]

Whenever my supervisor sends me an email thats encrypted to my personal hotmail email i click the verify signiture button,im on android galaxy s7, it says "unable to verify signature. Root CA certificates not installed." Where can i download these certs, i swear it worked on my galaxy s6.

 

[Mahesh Cherian]

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