Examples of good spam checker programs include MailWasher, Spamihilator and ChoiceMail. The first two are free, although MailWasher features a Pro versions that includes additional features such as recycle bin, preview pane and access to technical support 7 days a week. ChoiceMail requires a paid yearly subscription, but it provides updates and upgrades for free as long as the subscription is current.
As of 2015, MailWasher has more than eight million users and boasts compatibility with all popular email services, including Gmail, Yahoo Mail and Thunderbird, among others. With this program, users can mark email messages from specific senders as spam by clicking the thumbs down button, which instructs the program to automatically filter out messages from these senders in the future. It also lets users preview the content of an email message before downloading it. Other important features include options to create customizable filters, blacklists and whitelists.
Spamihilator uses Bayesian filtering to calculate the probability of an email message being spam. This allows the program to effectively block 98 percent of spam messages before they even reach the inbox. It lets users specify keywords, which results in the program blocking any email messages that contain those keywords. Unlike the other two programs, ChoiceMail includes a feature that lets users send a query to unknown senders before their message reaches the inbox, allowing users to block senders that refuse to respond to the query.