The move comes as a relief to IronPort customers, many of whom were unsure how Symantec's acquisition of Brightmail would affect the products.
"Enterprises and ISPs recognize the need to secure their email systems from the harmful effects of spam, viruses and other email-borne threats," said Enrique Salem, CEO of Brightmail. "With our expanded collaboration we will protect millions more mailboxes."
Under the new agreement, the firms are to target the ISP and SME markets.
IronPort, an email services company, and Brightmail, an anti-spam firm, will continue to sell to large enterprise customers. The IronPort-Brightmail solution has been deployed on more than 50 million internet mailboxes.
The partnership was first forged in July 2003.