At present, I am not aware of any desktop antivirus product (paid or free) that offers decent e-mail protection, at least not to the extent that Gmail offers.
For example, Malware distributors regularly distribute their infections as e-mail claiming to be bank statements, overdue invoices, voice messages, customer complaints and so on, which usually contain a zipped executable file attached. Now, can someone name just one desktop virus checker that can automatically quarantine e-mails that contain any executable files in its attachment?
As I own a domain name, I regularly get such e-mails, usually sent to non-existant e-mail addresses of my domain (support@, info@, etc.) and I usually upload the attachments to VirusTotal which checks them against 54 products. Generally just 2 to 4 of them show the attachment as infected and these 2 to 4 vary, so there’s no virus checker that detects them all. Usually if I retry the attachment a day later, the majority show it infected.
I do know many of the e-mail server based virus protection offer such attachment filtering, but very few consumers are going to run their own e-mail server just to get that type of protection, which is also quite expensive. Even businesses moving to the cloud lose out, as there’s no way to install e-mail server protection with most hosted e-mail services, such as Office 365.