Thank you for reaching out. There is not a way to link an anchor to an image using the image block. It may be possible to code that behavior in an image using the HTML block, but this is the only possibility. Anchor links don't behave consistently across the board for all the different web, desktop, and mobile email clients so I always encourage finding an alternative method of getting folks to read more. You might consider creating a shorter version of the newsletter and then linking out (by text or by image) to the entire version of the newsletter, which could be housed in the document library. That's the first suggestion that comes to mind, and I hope it's one you can use. Please let me know if you have any questions about this!
I just wanted to check in with you to make sure you don't still have questions! If there's anything I can assist you with please let me know. If I don't hear back from you I'll assume you're good to go for now. Thanks!