We recommend the usage of Mozilla Thunderbird for anonymous e-mail accounts and explained the reasons in the former blog post Secure your E-Mail Usage.

The Thunderbird add-on TorBirdy simplifies the configuration of Thunderbird and implements security features for anonymous e-mail usage. We offer a newer version for download with small bugfixes and improvements, which are not available in the TorBirdy release published on the Mozilla add-on page until now. Install instructions and download links you may find in our online help at the page Anonymous e-mail accounts with Thunderbird .