Use GMail as default email client on Linux / Ubuntu / Raspbian / Arch

gmail-mailto

#!/bin/sh

# Installation for using GMail as your preferred application
# This is for handling mime type: x-scheme-handler/mailto
#
# Place this script in your $PATH, and mark as executable
#
# Install the .desktop file:
#   cp gmail-mailto.desktop ~/.local/share/applications/
#
# Check your current handler:
#   xdg-mime query default x-scheme-handler/mailto
#
# Set your handler:
#   xdg-mime default gmail-mailto.desktop x-scheme-handler/mailto
#
# Write a test email to a friend:
#   xdg-email jon@rm-f.net
#

# open a new window (try fallbacks if others don't work)
URL="https://mail.google.com/mail?view=cm&tf=0&to=`echo $1 | sed 's/mailto://'`"
xdg-open $URL || sensible-browser $URL || x-www-browser $URL || gnome-open $URL

# A more direct route:
# firefox "https://mail.google.com/mail?view=cm&tf=0&to=`echo $1 | sed 's/mailto://'`"

gmail-mailto.desktop

[Desktop Entry]
Version=1.0
Name=Mailto Gmail
GenericName=Web E-mail client
Exec=gmail-mailto %u
Icon=gmail
Categories=Network;Email;
Keywords=mail;gui;gmail;pop;imap;smtp
Comment=Launches Gmail in your browser
Terminal=false
Type=Application
StartupNotify=true
MimeType=x-scheme-handler/mailto;
X-Info=Gmail Mailto
# TODO:
# Actions=GetMail;ComposeMail;SendFile;
#
# [Desktop Action GetMail]
# Exec=gmail-mailto --receive-all
# Name=Get Mail
#
# [Desktop Action ComposeMail]
# Exec=gmail-mailto --compose
# Name=Email...
#
# [Desktop Action SendFile]
# Exec=gmail-mailto --compose --attach %f
# Name=Send file...