I\'m sending a pdf through MFMailComposeViewController. The sender\'s signature is seen as an attachment when viewed in Outlook, but not the iOS native mail app.Everything else
After some more digging, this is an issue with the exchange server and not with Swift/ iOS/ etc. It has to do with the way that Exchange expects email content to be ordered. I haven't found a clear answer on if the newer versions of Exchange address the issue. The MIT link specifically mentions Exchange Server 2007 & 2010. Also, I was able to confirm that the issue is when the mail is being sent by Exchange, not received.
http://kb.mit.edu/confluence/pages/viewpage.action?pageId=4981187
https://support.microsoft.com/en-us/help/969854/the-body-of-a-message-is-shown-incorrectly-as-an-attachment-if-you-try