This problem is happening for one of our customers and I have been unable to replicate on my side using the same version of Outlook. My customer and I are using Office 365 with Outlook 2016 installed. When he sends an email in our program via Outlook Redemption (a third party program used for Outlook integration), the mail gets stuck in his outbox.

If he double clicks the message (so it pops up in Outlook) he can hit the send button and it will sucessfuly send. If they use an old version of Outlook (2010) this is not a problem. I upgraded them to the the newest version of Outlook Redmeption at the time (released May 07, 2016), though it looks like they just came out with a new version a few days ago. I'll try that soon, but the changelog doesn't mention mail getting stuck in the Outbox.

I also noticed that the emails in his outbox have what appears to be the 'draft' symbol on them, while in my outbox they have a 'sending' symbol on them. This seems important, but I'm not sure what I can do about that.

Also, hitting Send/Receive All Folders does not help.

My code is below. Thank you for any assistance.

```
        public static bool SendMessage(Recipients recipients, string[] addressListReplyTo, string subject, string body, string[] attachments, bool requestReadReceipt, Log log, bool isHtmlBody = false)
    {
        RDOSession session = null;
        RDOMail mail;
        RDOFolder folder;
        bool result = true;

        session = GetSessionAndLogon(log);
        if (session == null)
            return false;

        folder = session.GetDefaultFolder(rdoDefaultFolders.olFolderOutbox);
        mail = folder.Items.Add();
        if (isHtmlBody)
            mail.HTMLBody = body;
        else
            mail.Body = body;
        mail.Subject = subject;
        mail.ReadReceiptRequested = requestReadReceipt;
        foreach (string attachment in attachments)
        {
            if (attachment != "")
                mail.Attachments.Add(attachment);
        }
        foreach (string address in addressListReplyTo)
        {
            if (address != "")
                mail.ReplyRecipients.Add(address);
        }
        foreach (string address in recipients.To)
        {
            if (address != "")
                mail.Recipients.Add(address).Type = 1;
        }
        foreach (string address in recipients.Cc)
        {
            if (address != "")
                mail.Recipients.Add(address).Type = 2;
        }
        foreach (string address in recipients.Bcc)
        {
            if (address != "")
                mail.Recipients.Add(address).Type = 3;
        }

        foreach (RDORecipient recipient in mail.Recipients)
        {
            if (!OutlookMailEngine64.existsName(recipient.Name, session, log == null ? null : log))
                result = false;
        }
        if (result)
        {
            try
            {
                mail.Send();
                result = true;
            }
            catch (System.Runtime.InteropServices.COMException ex)
            {
                string message = "Error while sending email: " + ex.Message;
                if (log != null)
                    log.Message(message);
                if (OutlookMailEngine64.DiagnosticMode)
                    MessageBox.Show(message);
                throw new EmailLibraryException(EmailLibraryException.ErrorType.InvalidRecipient, "One or more recipients are invalid (use OutlookMailEngine64.ValidateAddresses first)", ex);
            }
        }
        if (session.LoggedOn)
            session.Logoff();

        return result;
    }

```