The charity, which employs only part-time IT staff, opted for the service after employees complained of receiving high levels of obscene emails.
Spam is a real problem for any organisation but the inappropriate content of many of the messages sent today is totally unacceptable," said Richard Blackwell, principal of the NCA. "It can be a nasty experience for staff particularly if they use the preview pane available in some email clients."
The Messaging Compliance & Security Group (MCSG) who supplied the service, BlackSpider MailControl Spam, said it enabled the NCA to filter out spam from 70 percent on some email accounts to virtually zero.
The managed service uses techniques including real-time black lists, Bayesian probability and trend analysis for detecting spam.
"When resources are at a premium it makes sense to outsource labour intensive chores," said Steve Adams, head of MCSG.
The NCA is an independent educational charity dedicated to training in the healing arts of Chinese medicine.