They are good readers. But. All are 6". Reading technical PDF on an ereader you will need a larger screen (9"). Check out Pocketbook's 9xx series. They will release a new FW soon and people seem to be happy with the RC pre-releases (annotation function improved).
I don't know about the support for right-to-left writing, but PB is known for it's openness. There are fonts, which support a very wide range of glyphs.
No reader will do email, maybe through the web browser, but not natively. Unless you get an Android based reader (nook, PRS-T1) and root it. Then you can install mail clients.
Ultimately, PDF with embedded graphics will be your goal. You could ask someone in the Pocketbook forum to check a file for you, if it displays all right. PDF is the worst format for ereaders and are a bit of a challenge to all of them.