username=my_windows_login
password=my_password
domain=my_domain

//myshare/myfolder /mnt/backup cifs credentials=/home/mydirectory/.Smbcredentials

mount error 13 = Permission denied
Refer to the mount.cifs(8) manual page (e.g.man mount.cifs)

chmod 600 ~/.Smbcredentials

//myshare/myfolder /mnt/backup cifs credentials=/home/mydirectory/.Smbcredentials,iocharset=utf8,sec=ntlm 0 0

mount -t cifs -o username=USERNAME,password=PASSWD //myshare/myfolder /mnt/backup