Edit image size that shows in email
There are size, alignment and padding options in the standard and Premium plugin.
Image size: Select from thumbnail, medium, large, any theme-specific sizes, and full size.
Size options display from your site's media settings. Premium provides an additional option to custom define a size.
How To Use It
Go to our plugin page from your WordPress dashboard, located in the left sidebar. The feature is set to thumbnail by default.
Select a size from the drop down.
To increase the image size, such as full width, choose a larger or full size image option. If the image is still too small or blurry, the issue is with the file or pixels size of the image itself, or the crop or ratio is not quite right. Upload a larger image to the post.
Remember to save your settings. If you are not immediately seeing the option take effect, clear your website cache or refresh your feed with the third party service being used to display your RSS content.
The size set from the plugin will show in Mailchimp (and other RSS services) when using the merge tag. The plugin alignment and padding settings require custom CSS to display in Mailchimp email.
Read: Padding or alignment settings do not show in Mailchimp?
Looking for other sizes? Size options display in the drop down from your site's media settings. Set the size of images for your website globally using "Media Options" to change these options. Then "Regenerate Thumbnails" for it to take effect.
Here's an easier way! The Premium plugin provides an option to enter a custom image size within the plugin settings.