我认为问题可能在于您使用 https 链接，但是您没有 TLS通道为他们设置。在Sendgrid的品牌链接帮助页面上确实很难解释，但是您可以看到它的提述此处。基本上，您需要可以解决TLS并将请求转发到sendgrid的东西。它可以是该帮助页面上建议的代理，也可以是一个云前发行版，其中的自定义来源指向sendgrid，证书覆盖了您的品牌链接域。

I think the issue might be that you that you use https links, but you don't have a "TLS pass-trough" set-up for them. It's really poorly explained on Sendgrid's branded links help page, but you can see a mention of it here. Basically you need something that will resolve TLS on your side and forward the request to sendgrid. It can be a proxy, as suggested on that help page, or i.e. a cloudfront distribution with a custom origin pointing to sendgrid and a certificate covering your branded link domain covered.