Sending an email from a redirected webmail account?

[#1]

I have set up a number of PlusNet email addresses that are re-directed to my main email provider, lets say joebloggs@virgin.net receiving emails that way works fine.
But, is it possible to send an email from an redirect email address I haven't been able to work out how to do it.
I know how to set up a separate mailbox in webmail to send & receive emails via PlusNet, I wondered if something similar is possible with a re-direct webmail address ?
Thanks.

[#2]

Log into Webmail and set up an Identity for each redirect address. Once you've done this, you'll see a drop-down next to the From field in the message composition window where you can choose the address you want to send from.

[#3]

It works. Thanks very much.