[quote user="MP."] Is there something like the filetype.pm, which checks outgoing files, for incoming files?[/quote]

Yes.  It is mime-map.pm.  As Michael said, this should not be needed if the extension is know to the system but I understand the benefit of removing "unknown" for user benefit (I have done it here).  Here are my instructions to self:

Quoted from the Pegasus Mail manual:

FILETYPE.PM -  Pegasus Mail uses this file to work out what attachment type it should associate with a given file. It is used when "Mailer decides" is chosen as the attachment type in the Attachments view of the Message editor. Having a well-stocked FILETYPE.PM file means that your messages are more likely to be sent with the information necessary to allow other programs to associate file viewers with them.  Instructions are contained within the file which is a plain text file.

MIME-MAP.PM - Pegasus Mail uses this file to translate custom MIME content types into attachment types. New MIME content types are being added all the time, and using this file allows Pegasus Mail both to generate them in outgoing mail and to recognize them in incoming mail. For example, say someone sends you a MIME message with the content type "Application/MyWordProcessor", and you have an entry that says that "Appli-
cation/MyWordProcessor" is the same as "MS-Word", then Pegasus Mail will be able to work out that it can run MS-Word to view the document.

Example to self:

Adding the following lines to FILETYPE.PM will identify the file type of .docx files as "MS-DOCX" and .xslm files as "MS-XLSX".

MS-DOCX,0,X,0,.DOCX
MS-XLSX,0,X,0,.XLSX

Taking this a step further, adding the following lines to MIME-MAP.PM will identify the file type in the Pegasus Mail reader Attachments tab as "Microsoft Office  Word Document" and" Microsoft Office Excel Spreadsheet".

application/vnd.openxmlformats-officedocument.wordprocessingml.document = MS-DOCX
application/vnd.openxmlformats-officedocument.spreadsheetml.sheet = MS-XLSX

NOTE:   "MS-DOCX" and "MS-XLSX" _MUST_  be the same text as the corresponding <file type>  entry that you have in FILETYPE.PM
 

Hello,

we often receive Mails with attachments, that are labelled unknown and Users don't know how to open them.

Is there something like the filetype.pm, which checks outgoing files, for incoming files?

Thank you

Michael

[quote user="MP."]

we often receive Mails with attachments, that are labelled unknown and Users don't know how to open them.[/quote]

They shouldn't need to know if the respective filename extension is registered in Windows. Which filename extension do the "unkown" files have? Pegasus Mail usually just hands the files over to the system which should "know" what to to with them from the extension.