[S-mailx] How download attachment of incoming mail?

[Χάρης Καραχριστιανίδης]

I received an email with a *.fit attachment. 2 problems: How can I download it? 
Ans 2nd when I open the mail with next mailx tries to read the attachment:
<?xml version="1.0" encoding="UTF-8"?>
<TrainingCenterDatabase 
xsi:schemaLocation="http://www.garmin.com/xmlschemas/TrainingCenterDatabase/v2 
http://www.garmin.com/xmlschemas/TrainingCenterDatabasev2.xsd"; 
xmlns:ns5="http://www.garmin.com/xmlschemas/ActivityGoals/v1"; 
xmlns:ns3="http://www.garmin.com/xmlschemas/ActivityExtension/v2"; 
xmlns:ns2="http://www.garmin.com/xmlschemas/UserProfile/v2"; 
xmlns="http://www.garmin.com/xmlschemas/TrainingCenterDatabase/v2"; 
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"; 
xmlns:ns4="http://www.garmin.com/xmlschemas/ProfileExtension/v1";>
 <Activities>
  <Activity Sport="Running">
   <Id>2023-02-27T11:17:18Z</Id>
   <Lap StartTime="2023-02-27T11:17:18Z">
    <TotalTimeSeconds>504</TotalTimeSeconds>
.....

Thank you!
Haris