Steps to reproduce:

1. Create an item with unit degrees Celsius (»°C«)
2. Create a trigger referencing this item
3. Configure an action to notify by e-mail about the trigger using a template containing {ITEM.VALUE} or the like
4. Cause the trigger to trigger

Result:

A conforming e-mail client displays the value's unit as »Â°C«. (C2 B0 43; the first two bytes are the UTF-8 representation of U+00B0 DEGREE SIGN.)
**

Expected:

The unit is displayed as »°C«.

This is caused by a regression in commit a3f13ee0 to src/libs/zbxmedia/email.c that removed the charset declaration from the Content-Type header of outgoing e-mail. This declaration was added (I think) in ZBX-391 back in 2008.