SendGrid返回202状态码但部分邮箱客户端未收到邮件的问题求助

我写了一段用SendGrid发送带CSV附件邮件的代码，用Gmail测试时邮件能立刻出现在收件箱，但换成CyberFolks这类客户端就收不到。SendGrid返回的响应状态码是202，看起来请求已经被正常接受了。

下面是负责发送邮件的代码片段：

SG_apikey = sendgrid_api

from_email = Email("my@mail.com")
to_email = To("my_friends@mail.com")
cc_mail = Cc("my_gmail@gmail.com")

subject = f"Orders from XXX for"
content = Content("text/plain", "Orders from XXX for can be found in attachment")

with open("orders.csv", "rb") as f:
    base = base64.b64encode(f.read()).decode()

attachment = Attachment(
    file_content=FileContent(base),
    file_name=FileName("orders.csv"),
    file_type=FileType("text/csv"),
    disposition=Disposition("attachment"),
)

mail = Mail(from_email, to_email, subject, content)
mail.add_attachment(attachment)
mail.add_cc(cc_mail)

sendgrid_client = SendGridAPIClient(api_key=SG_apikey)
response = sendgrid_client.send(mail.get())

print(response.status_code)
print(response.headers)

我已经尝试过以下几种方法，但都没解决问题：

• 修改MIME类型
• 检查邮箱地址是否拼写错误
• 多次确认SendGrid面板里我的域名已经完成授权/验证
• 测试过带附件和不带附件的发送情况

有没有大佬能给点解决思路？

备注：内容来源于stack exchange，提问作者Janek