Eudora

Eudora by Qualcomm is a specialized mail and news application based on Mozilla's open-source Thunderbird client. It's important to note that Eudora is not designed to compete with Thunderbird; rather, Qualcomm aims to complement it. The company is dedicated to preserving the Eudora user experience while maintaining maximum compatibility for both developers and users, especially with Thunderbird. By building a singular development community around Thunderbird and Eudora, Qualcomm plans to further advance both mailers at a much faster pace than before.

Eudora is essentially a branded version of Thunderbird that boasts some additional features developed by the Eudora team. Meanwhile, Penelope is an extension, or "add-on", that works with both Eudora and Thunderbird seamlessly. If you're installing Eudora, the corresponding version of Penelope will already be included. While most Penelope features can be accessed using Thunderbird, some require Eudora to function correctly. However, this particular requirement is not commonly tested.

When referring to the older versions of Eudora developed by Qualcomm in the past, some documentation may differentiate them from the current Thunderbird-based versions of Eudora. This is commonly done by labeling the older versions as "original Eudora" or "Classic Eudora."