Just configure a map for the enums:
Mapper.CreateMap<SourceClassification,DestinationClassification>().ConvertUsing(val =>
{
switch(val)
{
case SourceClassification.Required:
return DestinationClassification.Mandate;
case SourceClassification.Optional:
return DestinationClassification.Optional;
case SourceClassification.Selective:
return DestinationClassification.Selective;
default:
return <whatever the default should be>;
}
});
This has the benefit of being a flexible solution, so if either enum is refactored you will need to make sure to address the change in the conversion function.