Mimecast's managed e-mail service was implemented as part of the firm's business continuity plan.
Keoghs had been using a system that merely placed potential spam e-mails into a holding area, but these all had to be reviewed and legitimate e-mails released.
"IT staff had to manually check about 6,000 potential spam e-mails a week, which delayed legitimate e-mails and was a major drain on IT resources," said John Smith, chief information officer at Keoghs.
Smith said that unlike most other systems, Mimecast does not analyse content, but instead sorts e-mail based on a trusted-sender list.
"This means less than 0.05% of spam needs to be reviewed, the time e-mails spend in quarantine has been reduced from two hours a day to a matter of minutes, and the issue of false positives and genuine e-mails being blocked is practically eliminated," said Smith.
Keoghs chose Mimecast on recommendation from integrator Network Defence and several Mimecast users whom the law firm consulted, but its quick and easy deployment as well as the fact that it has freed up IT staff and improved the user experience made the choice a "no brainer", said Smith.