DBADash is unable to send email alerts

[sumandey89]

I have tried using port 587 and my SMTP server name and I could successfully send email using Powershell from the server where DBADash is installed. But while using the same port and server details on DBADash GUI. It is not able to send any email and the notification fails with the below error message. Can someone guide me on resolving this error.

Error Message:
MailKit.Security.SslHandshakeException: An error occurred while attempting to establish an SSL or TLS connection.

The server's SSL certificate could not be validated for the following reasons:
• The server certificate has the following errors:
• The revocation function was unable to check revocation for the certificate.
• The revocation function was unable to check revocation because the revocation server was offline.

---> System.Security.Authentication.AuthenticationException: The remote certificate was rejected by the provided RemoteCertificateValidationCallback.
at System.Net.Security.SslStream.CompleteHandshake(SslAuthenticationOptions sslAuthenticationOptions)
at System.Net.Security.SslStream.ForceAuthenticationAsync[TIOAdapter](Boolean receiveFirst, Byte[] reAuthenticationData, CancellationToken cancellationToken)
at MailKit.Net.Smtp.SmtpClient.SslHandshakeAsync(SslStream ssl, String host, CancellationToken cancellationToken)
at MailKit.Net.Smtp.SmtpClient.PostConnectAsync(Stream stream, String host, Int32 port, SecureSocketOptions options, Boolean starttls, CancellationToken cancellationToken)
--- End of inner exception stack trace ---
at MailKit.Net.Smtp.SmtpClient.PostConnectAsync(Stream stream, String host, Int32 port, SecureSocketOptions options, Boolean starttls, CancellationToken cancellationToken)
at MailKit.Net.Smtp.SmtpClient.ConnectAsync(String host, Int32 port, SecureSocketOptions options, CancellationToken cancellationToken)
at DBADash.Alert.EmailNotificationChannel.InternalSendNotificationAsync(Alert alert, String connectionString) in D:\a\dba-dash\dba-dash\DBADash\Alert\EmailNotificationChannel.cs:line 65
at DBADashGUI.DBADashAlerts.NotificationChannelBase.SendNotificationAsync(Alert alert, String connectionString) in D:\a\dba-dash\dba-dash\DBADash\Alert\NotificationChannelBase.cs:line 69

[sumandey89]

@DavidWiseman any help on this?

[DavidWiseman]

I would work with your IT team to determine why the certificate revocation couldn't be checked.

There is an option to disable this check (See here for more info), but I need to make it configurable and I don't have a way to validate the fix.

I have a branch with a potential fix and I've produced a build. Download and follow this process to upgrade manually.

After upgrading, edit the notification channel and change this option from true to false.

If the fix works, let me know and I'll include it in the next release.

[sumandey89]

Thanks @DavidWiseman . I will be applying the custom version on my environment next week and update you how it works.

[sumandey89]

@DavidWiseman I upgraded DBADash manually using the custom build but the email alert is still failing with almost similar error message.

[DavidWiseman]

Hi, did you remember to change this setting to false after the upgrade?

DBA Dash uses MailKit to send emails. https://github.com/jstedfast/MailKit

If you are able to do some troubleshooting and development for this, the mail implementation is here:
https://github.com/trimble-oss/dba-dash/blob/main/DBADash/Alert/EmailNotificationChannel.cs

My fixed version makes the following changes:
main...DavidWiseman:dba-dash:1273_CheckCertificateRevocationOption

Thanks,

David

[DavidWiseman]

PS. This is a list of mail providers I know for sure work.

Gmail
MailChimp (Mandrill)

From user feedback I know other people are successfully using email notifications and are probably using a variety of other providers.

I expect my implementation with MailKit will work in most cases, but there might be changes that can be made to improve compatibility. I'm open to pull requests as I might not be able to provide a fix myself if I'm unable to reproduce the issue. Hopefully it's just a case of setting the check certificate revocation to false - if that works or if you already tried it, let me know.

[sumandey89]

I double checked the settings recommended by you and I can confirm that I have modified the 'Check Certificate Revocation' to False. I tried multiple open ports on the SMTP server but unfortunately, I am still unable to use the send email alerts.
I am not an expert on coding. Hence I have to check with my IT team to further investigate the certificate revocation issue.