When you use the word 'identity' can you clarify what you mean? Do you have two mail accounts that display in the left Folder Pane, one for each email address and each mail account has it's own set of folders? OR Do you have one mail account displaying in the left Folder Pane, but it has an additional 'identity' - two email addresses going into the one mail account? If you have two mail accounts in the left Folder Pane, then it sounds like you have the second one using the default smtp which of course is a different email address and password. The second hotmail account needs to use it's own smtp server specifically for that email address. 'Tools' > 'Account Settings' > 'Outgoing server (SMTP)' or right click on mail account name in Folder Pane and select 'Settings' then select 'Outgoing server (SMTP)' see first image below. How many hotmail smtp servers are listed ? '''If there is only one default hotmail Outgoing server listed:''' You need to create a second one for the second mail account. Click on 'Add' Enter a suitable Description - this is only used by you to tell the difference between more than smtp server when server settings are the same. The server name, port, connection security and Authentication method will be the same as your first smtp hotmail server. enter the 'Server name' Enter correct Port number select connection security type Authentication method: Normal Password User Name : usually full email address. click on OK '''If you already have two hotmail Outgoing Server (SMTP):''' select the second (not default) one and click on 'Edit' Modify the 'Description' so it says something more meaningful that will help you identify it. click on OK '''Then you need to instruct your second hotmail mail account to use that second smtp server.''' Select the name of the mail account/email address in the left Pane. On the right side, near the bottom, you will see 'Outgoing server (SMTP). There will be a drop down selection showing the two outgoing servers. You need to select the correct smtp server. the description should help you to identify which one it is. click on OK the first time you try to send from your second hotmail email address/mail account using that selected smtp server, it will ask you for the password. Images below to help clarify where you should be doing the above. I had two mail accounts using a bt yahoo server. Later I added a third gmail mail account. All mail accounts use their own smtp server. Note: my details will not be the same as you use, but the place where it is done will be the same.