Strange prefix "ÿþh" in the mail when sourcing a value from a file

Hi,

I faced an strange issue when sending emails for one of the pipelines. 

I'm sourcing a value from a file, as it was easier way I found to inject it to mail body, nevertheless there is a prefix "ÿþh" in the mail, even do such symbols does not exist in text file I source, so it's clearly something related to the html conversion. 

Same plugin does work fine for other mail notifications without having this prefix.

Attaching some screenshots below.