Trouble sending as alias in AWS Workmail on iPhone

I have several Workmail aliases assigned to my main email address. Sending from aliases works perfectly on my desktop (using the AWS web client and Outlook 2016). But I cannot find a solution to send as alias from my iPhone. I've tried the iOS Mail, Outlook, Yahoo, Gmail, AirMail, Blue Mail, Edison, Spark, Spike, Canary, myMail, Superhuman Mail, Hey, Newton, and Polymail iphone mail clients. But none of them work. They either don't support sending from aliases or they don't correctly conceal my main email address. For example, when I send from myaliasaddress@mydomain.com the recipients receive an email from mymainaddress@mydomain.com instead which I don't want and defeats the purpose of using aliases. Can some please recommend an iPhone mail client that is compatible with AWS Workmail to send as alias? Thanks