SMTP中继
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SMTP中继是一个中间[[mail-server|邮件服务器]]，代表发件人接受来自应用程序的出站电子邮件并将其转发至收件人的邮件服务器。事务性邮件服务（SendGrid、Postmark、AWS SES）作为SMTP中继运营，提供具有既定发送声誉、投递分析和退信处理功能的专用IP。使用SMTP中继需要在域名的[[spf-record|SPF记录]]中添加其IP范围或include机制，并通过中继提供商配置[[dkim|DKIM]]签名，以确保从自定义域名进行已认证的投递。
示例
A Django application uses SendGrid as an SMTP relay: outbound mail authenticates as [email protected], passes through SendGrid's high-reputation IPs, and arrives in inboxes rather than spam — with full open/click tracking in the dashboard.