E-mail is still one of the most used attack vectors used. Many organizations are moving their e-mail to a cloud provider such as Microsoft, Office365 offers an Exchange in the cloud solution with some built-in security features.
We do see that the built-in security features of Office365 are not enough for most customers. Especially for blocking complex attacks you need sandboxing solutions where files can be executed before they are send through.
Another very important remark is that many organizations are looking for protection to fraud e-mails, also known as CEO fraud whereby typically e-mails are send on behalf of the CEO to transfer money to an external account. According to the FBI, this type of attack was the most successful, in terms of financial loss, for cybercriminals in 2016.