Some e-mails are sent using quoted-printable encoding [0], resulting in
notifications with weird characters.
This commit adds support for this encoding, resulting in the following:
**Before**
```
A
=3D=3D=3D=3D=3D
B
=3D=3D=3D=3D=3D
C
```
**After**
```
A
=====
B
=====
C
```
[0] https://www.rfc-editor.org/rfc/rfc2045.html