Here's an example of how you might concatenate email addresses from a table into a single @recipients parameter:
CREATE TABLE #emailAddresses (email VARCHAR(25))
INSERT #emailAddresses (email) VALUES ('[email protected]')
INSERT #emailAddresses (email) VALUES ('[email protected]')
INSERT #emailAddresses (email) VALUES ('[email protected]')
DECLARE @recipients VARCHAR(MAX)
SELECT @recipients = COALESCE(@recipients + ';', '') + email
FROM #emailAddresses
SELECT @recipients
DROP TABLE #emailAddresses
The resulting @recipients will be: