I just run the below srcipt and the email arrived with the backup file.
Run this first, if email not arrive check again with a gmail account like i did.
add name=test_mail policy=ftp,reboot,read,write,policy,test,winbox,password,sniff,sensitive,api source="#make the backup file\r\
\n/system backup save name=[/system identity get name];\r\
\n#wait 2 seconds\r\
\n:delay 2;\r\
\n#get name date and time\r\
\n:local name [/system identity get name];\r\
\n:local date [/system clock get date];\r\
\n:local time [/system clock get time];\r\
\n#make subject massage\r\
\n:local sub (\$name . \" - \" . \$time . \" - \" . \$date);\r\
\n#make body massage\r\
\n:local bod (\"See attached file for System Backup\");\r\
\n#send e-mail\r\
\n/tool e-mail send to=\"username@gmail.com\" subject=\$sub body=\$bod server=[:resolve smtp.gmail.com] tls=yes file=([/system identity get name] . \\ \".backup\");\r\
\n#show info message in log\r\
\n:log info \"Finish sending e-mail\";\r\
\n"