Email error after backup

I’ve run many Duplicati configs before but this is the first time I encounter this error.
I running Duplicati on Debian 11 and everything is working fine except for one thing and that is that it’s not sending an email after job completion. It’s not the SMTP settings because I’m using the exact settings on other devices too. The error that Duplicati throws at me isn’t telling me much:

{"ClassName":"System.TimeoutException","Message":"The operation has timed out.","Data":null,"InnerException":null,"HelpURL":null,"StackTraceString":"  at MailKit.Net.SocketUtils.ConnectAsync (System.String host, System.Int32 port, System.Net.IPEndPoint localEndPoint, System.Int32 timeout, System.Boolean doAsync, System.Threading.CancellationToken cancellationToken) [0x000d9] in <044c7cb38b61487086ccf0eae49cb447>:0 \n  at MailKit.MailService.ConnectSocket (System.String host, System.Int32 port, System.Boolean doAsync, System.Threading.CancellationToken cancellationToken) [0x00171] in <044c7cb38b61487086ccf0eae49cb447>:0 \n  at MailKit.Net.Smtp.SmtpClient.ConnectAsync (System.String host, System.Int32 port, MailKit.Security.SecureSocketOptions options, System.Boolean doAsync, System.Threading.CancellationToken cancellationToken) [0x0014f] in <044c7cb38b61487086ccf0eae49cb447>:0 \n  at Duplicati.Library.Modules.Builtin.SendMail.SendMessage (System.String subject, System.String body) [0x00581] in <41fe6492b6c947ad8a4acc2ac52d9c30>:0 \n  at Duplicati.Library.Modules.Builtin.ReportHelper.OnFinish (System.Object result) [0x00135] in <41fe6492b6c947ad8a4acc2ac52d9c30>:0 ","RemoteStackTraceString":null,"RemoteStackIndex":0,"ExceptionMethod":null,"HResult":-2146233083,"Source":"Duplicati.Library.Modules.Builtin"}

Hello and welcome…

I think this is the relevant part:

The operation has timed out.

Was this a one-off or does it happen every time?

I know you say the settings are exactly the same, but can you triple check… some things are easy to miss, like the server hostname URL being smtp://... instead of smtps://... (just an example).

Can you do a basic TCP connection test to the smtp server from the machine on which Duplicati runs? eg, telnet smtp-server port-number and see if it telnet connects or times out.

Hi, I figured it out. My VPS provider was blocking email ports, once I opend them it worked like a charm. I’m facing another problem now but I will create a new ticket for this. Thank you very much for your help! Greatly appreciated!