Images (avatar) are not shown in email notifications

Users images are not shown while acessing an email notification sent by FishEye 3.3.0.
This was reproduced both in Firefox and Chrome.
In the Mail application (Mac), the image is shown.

Steps to reproduce:
1) Create a review in FishEye 3.3.0.
2) Perform any activity that sends a notification.
3) Check it accessing the email in Firefox or Chrome.

I've attached screenshots showing the behavior.