If you are using Gmail for your email server then please setup your email configuration with these settings for communication
By selecting Gmail from from the account drop down it will populate the IMAP and SMTP settings required for Gmail.
You need to configure the Gmail email account to Allow Less Secure Apps to be turned on
Log into your Gmail account, select My Account, Device Activity and Set Allow less secure apps On
If you get the following error you need to use a gmail account that has the Less Secure Apps turned On.
Error sending e-mail: System.Net.Mail.SmtpException: The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.5.1 Authentication Required. Learn more at
at System.Net.Mail.MailCommand.CheckResponse(SmtpStatusCode statusCode, String response)
at System.Net.Mail.SmtpTransport.SendMail(MailAddress sender, MailAddressCollection recipients, String deliveryNotify, SmtpFailedRecipientException& exception)
at System.Net.Mail.SmtpClient.Send(MailMessage message)