At the price-point, Microsoft ATP is very good value and I have security industry peers that are using it themselves (in security consulting firms). Proofpoint and Mimecast have some pretty great additional features, but the increase in cost-per-user is substantial. Given the pricing for ATP and ease of implementation, it is worth trying it out for a few months and seeing if it addresses the issues rather than investing in a separate toolset that may not provide any better resolution to your current issues. It has been suggested too that additional time is spent configuring ATP (eg spam confidence thresholds), just to ensure that it is actually going to do the job you need. Given this advice, I have asked if there is any further information needed and ill await his reply next week.
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