FOR - Mark Hughes, MD (EMEA), Proofpoint

Monitoring outbound email benefits both employees and companies because it reduces the risk of confidential, sensitive or embarrassing digital content leaving the organisation.
While most data leakage is accidental rather than malicious, the eve of electronic information transfer means you must have a safety net to capture inappropriate content before it leaves the company. Without it, employees are a send button away from exposure because electronic messages are permanent, hold a lot of data and have been used in the courts and by the media.
Monitoring also protects the organisation's reputation and compliance with regulation. It also has the knock-on effect of supporting an appropriate work-life balance, as no employee wants their personal emails scrutinised.
Organisations need to have adequate messaging policies, and provide staff with a strong business justification for them. Ideally, employment contracts should make this clear, and staff handbooks should describe acceptable email practices. Finally, regular reminders that messages are monitored should be issued.
AGAINST - Graham Sadd, CEO, PAOGA
Do employers have a right to know what you're broadly doing during work hours? Absolutely. Monitoring someone suspected of illegal or commercially harmful activity is understandable, but should it be a legally enshrined right? Absolutely not! Emails that are clearly personal in nature should never be opened. If blanket monitoring is taking place, all staff should be told. Covert monitoring should only be used in order to detect or prevent a crime.
A government needs to protect its borders and citizens, but how would you react if it demanded access to all your mail, electronic or physical? The same applies in the workplace.
Companies want to protect themselves, from illegal activities and disclosure of trade secrets, but the vast majority of us are not criminals, cyberstalkers or porn addicts. We are respectable, law-abiding and policy-abiding. So respect us as individuals with a policy that monitors only those who violate that trust.
It is high time employers understand that respect for the individual is not a risky policy, but a good business strategy.