You specify the external application which is used to open attachments with the configuration option: attachment.external_open_cmd. Typical applications which detect the mime-type and figure out which application to open it with are xdg-open or exo-open.

When the process exits, astroid deletes the attachment, so if you have problems with attachment disappearing before they are opened you can use a wrapper script as below which waits for the file to be closed and also checks for viruses using clamav.

Put in e.g.: ~/.bin/my-xdg-open.sh and put the full path of the script into the config option: attachment.external_open_cmd.

#! /usr/bin/bash # # check for viruses and wait for file to be closed and for xdg-open to finish # # this script requires: libnotify, exo, clamav, inotify-tools # test for viruses (comment out this section if things go too slow and  # you are feeling reckless / trusting). if ! clamscan "$1" ; then notify-send "Virus detected" "Virus found in attachment, not opening!" --icon=dialog-warning exit 1 fi inotifywait -e close "$1" & ip=$! # open file (you can replace this with xdg-open) exo-open "$1" wait $ip # wait for file to be closed