If you get an 'alias' email on your phone which was forwarded to your main exchange acct. is there anyway to reply with that same email?

exchange@ main acct
mail@ alias acct =>> forwarded to exchange@

Need to reply via mail@ when received email via same.

I don't see that option anywhere; any suggestions?

I have set the mail@ as an acct on Tmobile pop3; the problem I have is I get 30 emails I read via BB; when I open outlook on the pc and it downloads those emails via POP3 it re-opens them on my BB. It's aggravating to say the least.
Any other suggestions?

Thanks