Due to financial difficulties, it appears that the end is near for Pegasus Mail.
While Pegasus has some great features, and is free, it is limited to Windows. This also raises the question of whether or not Pegasus users will be able to easily convert to other email programs. While most email programs can probably handle importing from Pegasus, there are also utilities to aid one in moving from Pegasus to other mail formats.
There are two good utilities, while Windows based, run well in Wine, or in various virtual machines on different operating systems. Both are developed by Fookes Software, Aid4Mail and Mailbag Assistant.
Both are able to convert from one email format to almost any other desired format. Aid4Mail can save messages to MHT format, for ease of viewing in a web browser. Mailbag Assistant is an email archiving and search utility. One can reply to or forward an email in any email box, using one’s current email program.
There is much more to both programs, that will help those with lots of email, from any program move to other formats. Both preserve the original mail files, so the conversion, is really a new set of files. These utilities make it very easy to investigate different email clients if one wants to experiment. Both are fast and can handle very large numbers of email messages.