UPDATE I tested this with Excel documents instead of PDFs, and it worked. Why won't it work with PDFs??

I am trying to add X amount of attachments to an e-mail by iterating over a list of file path strings. Instead I get X attachments, but they're all copies of the same file. So the amount of attachments is correct, but their content is not.

This happens even though:

1. the PDF files are saved correctly on disk.
2. whilst debugging, the list of file paths is correct.
3. whilst debugging, file names and file paths are distinct.

I am using FluentEmail to send e-mails. Also, I am building upon the following example (see 'Multiple attachments' section).

I added Debug.WriteLine(path) just to check if I am able to correctly output the strings in the loop, which I were.

My method:

public async void SendInvoicesEmail() {

    try {

        using (SqlConnection con = new(ConnectionString.connectionString))
        using (SqlCommand cmd = new("query text", con)) {

            con.Open();

            SmtpSender sender = new SmtpSender(() => new SmtpClient(host: "smtp.office365.com") {

                EnableSsl = true,
                UseDefaultCredentials = false,
                DeliveryMethod = SmtpDeliveryMethod.Network,
                Credentials = new NetworkCredential("email", "password"),
                Port = 587
            });

            Email.DefaultSender = sender;
            IFluentEmail newEmail = Email
                .From("email")
                .To("email")
                .Subject("subject text")
                .Body("body text");

            var attachList = new List<FluentEmail.Core.Models.Attachment>();

            // SourcePathList contains all the file paths I need to reference.
            foreach (string path in SourcePathList) {

                string fileName = Path.GetFileName(path);

                var attachment = new FluentEmail.Core.Models.Attachment {

                    Data = File.OpenRead(path),
                    ContentType = "application/pdf",
                    Filename = $"{fileName}"
                };

                attachList.Add(attachment);
                Debug.WriteLine(path);
            }

            newEmail.Attach(attachList);
            SourcePathList.Clear();
            FluentEmail.Core.Models.SendResponse result = await newEmail.SendAsync();

            if (result.Successful) {

                cmd.ExecuteNonQuery();
            }
        }

    } catch (Exception ex) {

        MessageBox.Show(ex.Message, "Message", MessageBoxButton.OK, MessageBoxImage.Information);
    }
}

I have tried:

1. Using newEmail.AttachFromFilename.
2. Using newEmail.Send instead of .SendAsync.
3. Iterating over array instead of list.
4. Changed my SMTP host.
5. Tried using ContentType for older PDFs (even though I have updated software): "application/x-pdf".

But none of the above made any difference.

The three items present are distinct, yet only the last item is added as file in the 3 attachments. Does ContentId matter?