外域入信失败原因

• • 什么是SPF？如何设置SPF来防止我的邮件被拒收呢？
• • 550 Mailbox unavailable or access denied
• • 501 Bad address syntax
• • 552 Message too large
• • 550 Mailbox not found
• • 550 Connection denied
• • 550 Mail content denied
• • 550 Ip frequency limited
• • 550 Domain frequency limited
• • 550 Sender frequency limited
• • 550 Connection frequency limited