Microsoft Outlook has a long rich history of doing annoyingly nonstandard things with email. Email is supposed to obey certain standards. Microsoft has tended to have the attitude that whatever they do is, by definition, the standard.
• there's some kind of forwarding of email that results in the recipient receiving a file attachment that Outlook understands but other email programs (and nonWindows operating system environments in particular) have no clue about.
• there are reciprocal problems with Outlook users being unable to open file attachments (JPG and etc) send by non-Outlook users; I don't recall the details but they get unrecognized files with strange extensions instead of the original file w/ original extension, usually some garbled 'mim' file
• strange approaches to encrypted connections, passwords, relationships of login accounts to email accountnames, designations of SMTP servers, etc — this really has more to do with MS Exchange Server than MS Outlook I suppose, but it's a way of practically forcing folks to use Outlook if their company is using Exchange Server. PITA to use some other email app to use with Exchange Server.
