Please add a third tab to the Control Panel -> Mail Server configuration named SMTP Relay, with a check box to Enable SMTP Relay and fields to enter SMTP server, username, and password. Use that information to configure Postfix as in this "Simple Guide"
Many Synology users are on residential networks that require SMTP relaying. This would preclude them from having to manually edit the Postfix configuration file.
DS 1512+ w/3GB, 5 x 3TB Seagate ST3000DM001 8.2TB RAID 6, half files/half Time Machine.
Icy Dock MB559U3S-1SB enclosure w/4TB Hitachi UltraStar via USB 3 for files backup
UVERSE to AirPort Extreme + 2 AirPort Express w/speakers. TRENDnet TV-IP312WN camera
CyberPower CP1500PFCLCD Sine Wave UPS
DSM 4.1-2661 w/SSH + SFTP, VPN Server, Syslog Server, Media Server, Mail Server, Mail Station,
Audio Station, Surveillance Station, Photo Station, Web Station - DS Apps on iPad & iPod Touch.