If you are having email account on self hosted server for own domain name then you must think about ways to protect your ID from Spam, Phishing mails, viruses etc. You email accounts should have proper protection layer to filter these spam and viruses. There are few paid services which does the same for your email accounts or you may choose to host your email accounts on Google Apps which offers 1 GB of email data storage.
Whether you are hosting your account on well managed hosting service provider for shared hosting or virtual hosting or dedicated one, you will have to have a filter (in case you are dealing with some critically important emails) for your email security. There are lot many exchange spam filter services available on hosting service provider’s account which can filter your email account for spam, phishing mails etc.
Email spam protection services actually passes your incoming emails thru their server and filter out spam, fraud emails, viruses etc in between. And finally your inbox will have scanned emails only. Yes, you should only use trusted services for this purpose as your emails are actually passing thru their system so that may cause privacy concerns.
Anyway, the suggested advice is that either you should use Google Apps like services where filtering is done in better way or you can use any trusted service to filter out spam in between and have scanned and protected emails only.