mail send using smtp.office365.com failed

Hi I'm used to send mail from asp.net mvc,C# code but the problem is its not work from site which start with HTTP, not any problem for send mail from site start with HTTPS. I didn't get what's the problem for this issue. I'm used below code for send mails

var hostEmail = ConfigurationExtensions.GetAppConfigValue("SMTPUserName").ToString();
var hostPassword = ConfigurationExtensions.GetAppConfigValue("SMTPPassword").ToString();
var fromEmail = ConfigurationExtensions.GetAppConfigValue("EmailFrom").ToString();

SmtpClient ss = new SmtpClient
{
    Host = ConfigurationExtensions.GetAppConfigValue("EmailHost").ToString(),
    Port = ConfigurationExtensions.GetAppConfigValue<int>("smtpPort"),
    Timeout = 20000,
    DeliveryMethod = SmtpDeliveryMethod.Network,
    UseDefaultCredentials = true,
    EnableSsl = true,
    Credentials = new NetworkCredential(hostEmail, hostPassword)
};

MailMessage mailMsg = new MailMessage(hostEmail, email, subject, msg)
{
    From = new MailAddress(fromEmail, mailname),
    IsBodyHtml = true,
    DeliveryNotificationOptions = DeliveryNotificationOptions.OnFailure
};
ss.Send(mailMsg);

My config code send below

<add key="EmailHost" value="smtp.office365.com" />
<add key="EnableSsl" value="true" />
<add key="smtpPort" value="587" />
<add key="SMTPUserName" value="email address removed for privacy reasons" />
<add key="SMTPPassword" value="password" />
<add key="EmailFrom" value="email address removed for privacy reasons" />
<add key="EmailUser" value="Test User" />
<add key="EmailID" value="email address removed for privacy reasons" />

Error screenshots attached below https://i.stack.imgur.com/L3j43.png https://i.stack.imgur.com/4hTU1.pnghttps://www.globalfintechleaders.com/

Also checked this issue in different sites but not get the solution. Problem only exist while sites start in http:, not any issues in https:
Anybody know the solution ? please help me to solve this issue.

Thanks in advance