Thank you.
It turns out, the path was the main issue.
After changing the path from "\my documents\sensordata3.txt" to "my documents\sensordata3.txt" it partially worked.
Meaning it sends the attachment just fine.
However, if a "sent from email address" is included with vi, then it do longer sends any email.
Also, if the attachment is 140kbytes, it gets truncated to 20kbytes, and is unusable.