ASP.NET Core Web API hosted on Azure don't send an email

Question

I have an Web API based on ASP.NET Core and hosted on Azure as App Service.我有一个基于 ASP.NET 核心的 Web API 并作为服务托管在 Z3A580F142203677F1F0ZBC308 上。 I have a simple functionality for sending an email.我有一个发送 email 的简单功能。 But it's only working on the localhost.但它只适用于本地主机。 When I publish it on the Azure, the POST query returns me error: 500.当我在 Azure 上发布它时，POST 查询返回错误：500。

It's a MailKit.Net.Smtp library.这是一个 MailKit.Net.Smtp 库。

    {
        [HttpPost]
        [AllowAnonymous]
        public async Task<ActionResult> SendMail([FromBody] Receiver receiver)
        {
            var message = new MimeMessage();
            message.From.Add(new MailboxAddress("Step OSBB", "receiver@gmail.com"));

            message.To.Add(new MailboxAddress("User name", receiver.Email));

            message.Subject = "Henlo, it's a testing email";

            message.Body = new TextPart("plain")
            {
                Text = "I am using MailKit to send this message"
            };

            using (var client = new SmtpClient())
            {
                client.Connect("smtp.gmail.com", 587, false);
                client.Authenticate("myemail@gmail.com", "mypass");
                client.Send(message);
                client.Disconnect(true);
            }
            return StatusCode(200);
        }
    }

    public class Receiver
    {
        public string Email { get; set; }
    }```