> P.S. Alessandro, could you, please, response to mails using "reply" > button. You messages lack of In-Reply-To and References headers, so at > least thunderbird does not group messages into a thread. Sure, no problem. I usually use vanilla compose-mail to answer, probably that's the problem. I am now trying directly with Gmail, let me know if it's working now. As I wrote in a previous answer, right now I simply set up Citar to use Sioyek by default: (setq citar-file-open-function '(lambda (file) (call-process "sioyek" nil 0 nil file))) This is not a problem since, when opening a citation, I would most likely want to use Sioyek for it. However, you gave me nice ideas to further explore. I'll have a look at mailcap and see if the script is worth being set up. I'll let you know if I discover something useful! In any case, thanks for your answer! Alessandro