We currently use Azure AD Connect to sync between our on-premise AD and 365.

Because of this sync we cannot add aliases directly in 365. We need to use ASDIEdit on our local domain controller and manually add an SMTP entry under the Proxy Address attribute. 

Would there be any way to do this in AD Manager when we using an import template? We would want this to be in the format of "SMTP:firstname.lastname@domain.com"