WSO2 EI 6.5.0 Send email with attachment - email

Question

I have a need to send pdf/png/jpeg files to emails via WSO2 EI 6.5.0
I have a proxy:
<?xml version="1.0" encoding="UTF-8"?>
<proxy xmlns="http://ws.apache.org/ns/synapse"
name="EmailService"
startOnLoad="true"
statistics="disable"
trace="disable"
transports="http,https">
<target>
<inSequence>
<log level="custom">
<property name="[EmailService] Initialize" value="SendMailSequence"/>
</log>
<property name="Subject" scope="transport" value="WSO2 EI Testing"/>
<property name="transport.mail.bodyWhenAttached"
scope="axis2"
value="This text will appear in body"/>
<property name="enableMTOM" scope="axis2" type="STRING" value="true"/>
<log level="custom">
<property expression="/" name="[EmailService] Before Send"/>
</log>
<property name="FORCE_SC_ACCEPTED" scope="axis2" value="true"/>
<property name="OUT_ONLY" value="true"/>
<property name="messageType"
scope="axis2"
type="STRING"
value="multipart/form-data"/>
<send>
<endpoint name="FileEpr">
<address optimize="mtom" uri="mailtoOwn:listopadov_as#kk.bank"/>
</endpoint>
</send>
</inSequence>
<outSequence/>
</target>
<description/>
</proxy>
I am trying to send a file (a cachier cheque) using Fiddler:
POST http://localhost:8280/services/EmailService HTTP/1.1
Content-Type: multipart/form-data; boundary=NewBoundary
--NewBoundary
Content-Disposition: form-data; name="attachment"; filename="cheque.png"
Content-Type: image/png
<...binary data...>
--NewBoundary--
And I get this in the WSO2 EI 6.5.0 console:
[2020-09-07 16:24:19,136] [] INFO - LogMediator [EmailService] Initialize = sendMailSequence
[2020-09-07 16:24:19,138] [] INFO - LogMediator [EmailService] Before Send = <?xml version='1.0' encoding='utf-8'?><soapenv:Envelope xmlns:soapenv="http://www.w3.org/2003/05/soap-envelope"><soapenv:Body><mediate><attachment filename="cheque.png">iVBORw0KGgoAAAANSUhEUgAAABgAAAAYCAYAAADgdz34AAAFwUlEQVR42rWWaWxUVRTHz3nLvJl5nZkuTBcoVHYqixpMUBCDRgUpoEBcQkICo2DZGmyjCRqEgKBWC9awFdLGhJCoIahoUBMNGjYDJBIRKpCCNKW0pdN2On2zvveO591SLKQf/KA3uTNz37v
3/M4593/PHYT/uaHz0ZSXJ8l5ebPNWGy6nUpJfS/pnsk0wPN7n6Gq2m6v9xiFw0cKm5ttAbhRXDxX37z5q87mZslKp/vmY7+12M9g31h80z1zGEDZBQVkbNjw/LCLF78RD//IyfmQysoqaPDg/yYtiQQkN26sejgcfkMATsvyNlixYq0yapQYW0RU39WFI3w+8CrKXRHAPRHETBOuRqNUnJmJMop
pRLEYRtev3z7DssrFk1Oy/DEtXVomDx+ONo/bcnPpkXnz8PeTJ0G7cIE0xAEBSSJMjh8Pk6ZOpV8PH8bctjbgDSQ0TYxs2lT9tGWtFQuPSdIn9qJFq6WiIkDu4xYsAEVR2BWCc8ePc4inQbHtu9KQZiZOmQIPTJsGkiSByZHUHzoEcP06KPwusnXrjlm2XSYARyVph71w4UqpsBBVXYdxoRDJWVl
os1HLsujS2bOYPHoUZDbieG4pCrpmzKAxkyejLMuOM2R1duKfdXWQNgxSNQ27Kit3zrHt1QLwI+Iua86cUiwoEGOXz0fFpaUoZWYKAHdsPH8e4t9/K1TkmVmCQydMIPZcALC7m+prajAVjQoH3H4/dlZV7X6OaCVWcT7HA+yyZs58DYLBOynQ/D4Yv2YNUEBAwInm1pVLIm05I0eDsy1OapSeKNT
v3AnJ7uidtTrbCW/fXtMNsBI/YsA4gD3Wk08sY2MiAgmBVAXQmx2A0avLKe0L9KXLAYhN5kaaEcWru6sh1hGhtAmo6BngCgQo1tKC8YMH9zKyFCt58liAvcb9xa8Ae+vSvaB5FHCpnCoFwJudCUNWvAkJPSCicLrD0M0khA/UQE9LKySMJBgRA8INjdDZcBXUDB0G9Ri1BsByfJcBxQD72gO+UDQ
SRbdHBp9fowy/G726Cuj3kfXqOhzz6OMiAmdPuGHzuTMU27wKKRqDeAoonuQzkQBIpoG0TD/6u7prOYJlAsAR7OvICYRinRH0utlrN5CuAcp+D5irNtODJfPRMe5I0QFwFOhQGk/9glC9DsxIjGIMMBjAEFKzM1Fv73Ii6AWMZkAkLzuU6OjADA9vkgbkyvKiWvEBTJw1T6jIMa53NglA2DNIAFw
uFzafOQHGe+WU6jSQMwU9cSA5Jxs9LR21sT7AKAZEhwwKpdrbwQF4snXI2lANE54pgT7PPeHrIFW+4BQCSLx+ALoyCoABoGkaNJ0+DjfXlUIs3OMAQA4OAqWpvS7RBxjBgHhRbijV2oZ6MAOKKnfTRNb6beOktl5FeH8+uONtQucJTxDTFV9QMjgcb0Po2omfsX7VEui5FSU5Pxfhr7baZB/gPga
kRuaFks2tyKcYHtqyTUhRKObGFYq9Mxc9iTbQ3b21iHONcS1I7o1fozR0LPBhI0e3v71dDvW1taQOyUOrobU2RbcBRQwwx+SH4o0t4PerMK1mP2Q/+SxYjZehpaIENPbcw8bdau9BSvCVEXcU4wlCftURkIeNgY6j38GJ5YuhuzsNWlE+mJdb6u4AhjLALi4IGQ03Uec98PlUGhsqxehPn4HLuEW
sKtRcAKrcG0HaAkyyNFkxmPIGwffUy3Spbg9Go2kweJO9o/IxXd9Sm3YAWxyAqu6BSYXLOs5dEwBHRY5RIVn+7WHJOgdP7r1MybLZcPq29pO90nRgjoocQOaEQkxfuLk3ZVqlojR8qbkWp2ZP/zTR1IASn1AuE3d1hT3nsuOUENFs3iGGgGlx2Tb/6SnuJnCZ92eR/8SFJS+a1n6x5AeuCoamvtQ
F9JiZNuWBLvqB/gQM1GRZsgIEx/2m/fksZva/qWCro5x/aWjAu9gplNzf6mfib96T0koiuIbpAAAAAElFTkSuQmCC</attachment></mediate></soapenv:Body></soapenv:Envelope>
And in result I get the cheque.png file but it is corrupted because the data inside is base64 encoded and even if I decode it manually and insert decoded data back into the file the file is still corrupted so there is no way I can view it.
I tried several other options and tried placing base64Decode in the payload:
<payloadFactory media-type="xml">
<format>
<root>
<file filename="cheque.png">$1</file>
</root>
</format>
<args>
<arg evaluator="xml" expression="base64Decode(//*[local-name()='attachment']/text())"/>
</args>
</payloadFactory>
But still nothing helps.
Please help me with a working example of how to send a file over email in WSO2 EI 6.5.0
My axis2 messageBuilders are set and the MailTransportSender is uncommented and works fine.