Add the possibility to give additional options to the mail command. Based on contribution from @f-andrey.

duplicity-backup.conf.example

@@ -387,12 +387,21 @@ EMAIL_SUBJECT=
 EMAIL_FAILURE_ONLY="yes" # send e-mail only if there was an error while creating backup
 
 # command to use to send mail
+# don't put any options here, as ${MAIL} is used to check if the command is available
+# on the system and locate its binary
 MAIL="mailx"     # default command for Linux mail
 #MAIL="mail"     # for CentOS, if "mailx" fails try this one
 #MAIL="ssmtp"
 #MAIL="sendmail"
 #MAIL="msmtp"
 
+# Array to pass additional options to the mail command
+# the options will be passed immediately after the name of the mail command
+# like this: ${MAIL} ${MAIL_OPTIONS[*]} ${other options}
+MAIL_OPTIONS=()
+# for example with mailx, you can set the server and port for sending mails like this
+#MAIL_OPTIONS=(-S smtp="smtps://mailserver.example.com:587")
+
 # You may specify a custom mail script instead.  It will be called with
 # the following convention:
 # MAIL "SUBJECT OF MESSAGE" "TO EMAIL ADDRESS" "FROM EMAIL ADDRESS"

duplicity-backup.sh

@@ -375,6 +375,7 @@ email_logfile()
       if [ ! -x "${MAILCMD}" ]; then
           echo -e "Email couldn't be sent. ${MAIL} not available." >> "${LOGFILE}"
       else
+          MAILCMD="${MAILCMD} ${MAIL_OPTIONS[*]}"
           EMAIL_SUBJECT=${EMAIL_SUBJECT:="duplicity-backup ${BACKUP_STATUS:-"ERROR"} [${HOSTNAME}] ${LOG_FILE}"}
           case ${MAIL} in
             ssmtp)