Please add these options as a native feature of thunderbird. There are multiple posts around the internet searching for it and even add-ons made to workaround this issue.
Not having these options greatly reduce the user-friendly aspect of the software, it is an e-mail client and is supposed to be opened at all times to check and receive new e-mails... I shouldn't have to search for an third-party add-on just to make this work even if the add-on code is reviewed by mozilla, I am trusting my e-mail access to it and this is key to multiple sensitive and personal info.
Please make this a feature