Hi,
did you manage to find a solution?
We are expreriencing the same issue: emails coming from Outlook loose their body when imported as ticket.
We came from a previous installation which has been working for several years, through various upgrades starting from 1.10.3 till 1.16
Now that we upgraded to 1.18.2, changing machine with upgraded requirements and importing the old database, we started experiencing this issue.
Our environment:

We noticed this issue beeing reported several times across the years but none of the proposed solution seem to work.
It seems that in the past someone solved by setting the constant MAIL_EOL to "\n". No effect for us.
Some other one disabling piping, but it seems this can't even be done now.
By the way, we also tested different emails directly piping them as text from command line and the behaviour is the same: eml originating in recent version of Outlook ("16" which should be from 2016 to 365) generate "(empy)" bodies, while eml coming from other mailers or oldest outlook (header X-Mailer claiming Microsoft Office Outlook 12.0 which should be 2007) get perfectly imported with regular bodies.