Email security provider Mimecast said it was the victim of a cyber attack that prevented some U.S. customers from accessing email on Monday.
"Mimecast experienced malicious traffic from multiple IP addresses, targeting its U.S. network. This resulted in service disruption for U.S. customers," Mimecast Chief Executive Peter Bauer said in a statement on Tuesday.
The statement said that service had returned to normal and that the attack appeared to be limited to disruption of email service for its clients.
The company declined comment when asked who was behind the attack or if law enforcement was investigating. An FBI spokeswoman said she had no immediate comment.
Mimecast's customers include software maker NetSuite Inc, advertising and marketing giant Omnicom Group Inc, Bon Pan restaurant chain, the Boston Celtics basketball team and the Cleveland Indians baseball team.
Its competitors include Proofpoint Inc and Symantec Corp.
