Mail Message Body With Data From Two Tables

I need to set a trigger so that an email is generated when a row is inserted into the ABC_DB_OnlineFormsConfirm table. The message will include data not only from that table, but from a related table called ABC_DB_OnlineForms. The common field between the two is FormID. This is related to an online account application process where the user has the option of completing it in one session, or saving it and coming back at a later time. Once the user has completed the first screen and clicks continue, a record is written to ABC_DB_OnlineForms. At the very end, when he clicks “Save and Complete”, a row is written to the ABC_DB_OnlineForms table. I would like the body of the email to include three separate lines, as follows. The first two pieces of data come from the OnlineForms table and the third from OnlineFormsConfirm. The field names are userid, IRSBackup and ConfirmationCode.

UserID:
Subject to IRS Backup Withholding?:
Confirmation Code:

What I have below results in an email body that contains the confirmation code all by itself. If I switch @body=@MessageBody to @body=@UserID or @body=@Backup, it will report the correct single piece of data, but I have no idea how to get all three pieces at once as separate lines including the leading descriptor (UserID:, Confirmation Code, etc.).

CREATE TRIGGER SendEmail
ON [ABC].[dbo].[ABC_DB_OnlineFormsConfirm]
AFTER INSERT
AS
Begin
Declare @MessageBody varchar(100)

[code]...