Willing to bet that your mail system is configured in a suboptimal way such that the email gets scanned for virus/spam once per recipient instead of just once over all.
Internal to internal mail shouldn't even need spam filtering. Should probably have virus scanning on though to stop the spread of malware through an org.
Internal to internal mail shouldn't even need spam filtering. Should probably have virus scanning on though to stop the spread of malware through an org.
Or could be something entirely different.