You speak of "more features", yet you address just one: knowing when someone has read your mail. First of all why do you need to know exact time when someone has read any particular mail - would it not satisfy you, if you just could see unread/read by recipient? In my opinion, there are much more demanding issues with mail-system, whereof most are written here: https://warlight.uservoice.com/forums/77051-warlight-features/suggestions/10945080-upgrade-mail-system
If this is what you need, just give your votes and maybe after a awhile Developers will pay attention to it.
Just to let you know, it is somewhat regarded private and even strategic information, the time one reads a mail or when one is online and does not commit orders - maybe a bargain is at hand and this would a hint to third player. I don´t think adding time-stamps or read/unread to mail is necessary. If you send a mail to someone who ends up not reading it - then obviously the problem lies somewhere else.