The most appropriate scenarios to implement email security is in companies that want to protect the use of electronic mail since it is one of the security breaches that are currently used to perform any type of attack. Very effective integration with Office 365 and it is highly recommended to add the functionality of advanced malware protection
It is very well suited for an organization that wants to protect inbound email and use just one product. It may be less appropriate for an organization that is small or has a limited IT support staff.
Cisco TAC support is very good since they have engineers available 24 hours a day, 365 days a year. Important to mention that you must have the support of the solution enabled to be able to receive a response from TAC and that we can be taken care of. The only drawback may be that they will not be able to see settings of the email provider you use.
Cisco was at least better than or equal to the others but within our budget. It provided all of the services of anti-spam, content filtering, anti-virus, DLP, encrypted email service, scalability, and more than the others. Cisco name and reputation were also key in our decision.
It would be difficult to determine the exact ROI Symantec Messaging Gateway had on your overall business. However, I can assure you the downtime suffered due to inbound email threats has been reduced to nearly zero in our environment. If IT isn't chasing down ransomware/phishing issues and users aren't staring at a quarantined PC, life is good.
There are no negative impacts on ROI that I can think of.