According to the manual you can export from Sylpheed to an MBOX format.
14.4 Exporting from Sylpheed MH format to mbox
Sylpheed offers a way to export a mailbox to the standard mbox format through the
File menu. Just select the "Export to mbox file..." option and you can select the
folder to export (assisted by a browse dialog) and also select or enter the name
of the mbox file you wish to generate.
WinPMail can read the MBOX file format so you should be able to export and have WinPMail read the MBOX files and move the messages to Pegasus Mail folders. From the help.
Unix Mailbox Format Folders
The so-called Unix Mailbox Format is a folder layout originating, as its name suggests, from the unix operating system. The primary advantage of this format is its pervasiveness - it is widely-supported by other mail programs, and hence is a useful import/export format. Unfortunately, it's also a very poor folder format, because it is badly standardized and used in different ways by different programs. Not only is it impossible to determine the boundaries between messages in a unix mailbox format folder with absolute reliability, the nature of the format means that many mail programs are forced to alter the actual body of many messages to accommodate it (this is why you'll often see lines starting with the word "From" rendered as ">From" in this format, although Pegasus Mail does not itself perform this particular defacement). We strongly recommend that you avoid using this format for anything except import and export. Pegasus Mail expects a Unix Mailbox Format folder to have the extension .MBX, and builds its own index for the file, which has the same name part as the master file, but the extension .PMG.
<p>According to the manual you can export from Sylpheed to an MBOX format.</p><h2><u><i><a class="" name="ss14.4"></a>14.4 Exporting from Sylpheed MH format to mbox</i></u>
</h2>
<p><u><i>Sylpheed offers a way to export a mailbox to the standard mbox format through the
File menu. Just select the "Export to mbox file..." option and you can select the
folder to export (assisted by a browse dialog) and also select or enter the name
of the mbox file you wish to generate.
</i></u></p><p>WinPMail can read the MBOX file format so you should be able to export and have WinPMail read the MBOX files and move the messages to Pegasus Mail folders.&nbsp; From the help.</p><p>&nbsp;</p><p><b>Unix Mailbox Format Folders</b>
The so-called Unix Mailbox Format is a folder layout originating, as its name suggests, from the unix operating system. The primary advantage of this format is its pervasiveness - it is widely-supported by other mail programs, and hence is a useful import/export format. Unfortunately, it's also a very poor folder format, because it is badly standardized and used in different ways by different programs. Not only is it impossible to determine the boundaries between messages in a unix mailbox format folder with absolute reliability, the nature of the format means that many mail programs are forced to alter the actual body of many messages to accommodate it (this is why you'll often see lines starting with the word "From" rendered as "&gt;From" in this format, although Pegasus Mail does not itself perform this particular defacement). We strongly recommend that you avoid using this format for anything except import and export. Pegasus Mail expects a Unix Mailbox Format folder to have the extension .MBX, and builds its own index for the file, which has the same name part as the master file, but the extension .PMG.
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