WLM Home/Work outgoing mail servers

Hello,

At work and at home I got different ISP's. So I can't send mail at work with my mail-account. Can I use multiple outgoing mail servers for 1 mailadres? If not... I've made a second account which is the same but with the other outgoing mail server. But when I create a new mail, I can select an account from where I send it from, but I only see the mailadresses. So I don't see which mailadress has the right outgoing mail server. Aliasses are shown in this dropdownbox for Outlook Express but not Windows Live Mail.
How I deal with this?

Usually an ISP has an authentication format for the server information so that if it is relayed through another server it will still be accepted. I guess it depends on which ISP is doing the blocking. If it's the remote server, the authentication format should work. If it's the local server, you might ask them why they are blocking it.