Just today we've created an account cs@decadeint.com, which after very settings starts working with Outlook Application. But not working with our Company Application which is used for Customer Support. Here is a copy of code from where actually a mail is send to client;

Dim SMTP As New System.Net.Mail.SmtpClient(Host, Port)
SMTP.DeliveryMethod = Net.Mail.SmtpDeliveryMethod.Network
SMTP.DeliveryFormat = Net.Mail.SmtpDeliveryFormat.International
SMTP.UseDefaultCredentials = False
SMTP.Credentials = New System.Net.NetworkCredential(CredentialUserId, CredentialUserPassword)
SMTP.EnableSsl = EnableSSL
SMTP.ServicePoint.MaxIdleTime = 1
MailMsg.From = New System.Net.Mail.MailAddress(CredentialUserId, SenderDisplayName)
SMTP.Send(MailMsg)

This code is working fine with all other email services like Gmail, Yahoo, etc. But is not working with Zoho Mail Service.