If you are using Advanced email templates (available in your account at cusrev.com), alignment of images works out of the box. On the other hand, Basic email templates do not have built-in support for centering images. Even though the visual editor provides buttons for aligning images and these buttons seem to work in the editor, the images will NOT be centered in email messages.
The technical reason why images do not get centrally aligned in emails is that WordPress uses special CSS classes for centering images in the visual editor. However, these CSS classes are not available in email clients, so central alignment is not applied to the images.
If you would like to continue using Basic email templates and add images aligned to center, it will be necessary to edit templates in "Text" mode and insert inline CSS rules. Some basic programming skills will be required to do it. Here are the steps to follow:
1. Click on Text tab in the editor to switch it to the Text mode.
2. Locate the HTML code related to the image (it can be identified by "img" tag).
3. Enclose the image into a "div" element with an inline CSS style for alignment to the center. To do this, insert <div style="text-align:center;"> before the image tag and </div> after the image tag. The HTML code in our example will look like this:
<div style="text-align:center;"><img class="wp-image-345 aligncenter" src="http://localhost/wp-content/uploads/2020/04/371.jpg" alt="" width="99" height="99" /></div>
4.Switch back to Visual mode in the editor and save settings.
5. Send a test email (use Send Test field on Review Reminder tab of the plugin's settings) to verify that the inline CSS style works as expected.
If you would like to avoid coding, try using the Advanced email templates (available in your account at cusrev.com). They support changing of image alignment without any coding and offer additional customization options.