Error sending email using CDO on port 587 (TLS) - c++

Question

Is there any trick to sending mail with CDO on port 587 (the port that uses TLS security protocol)?
This is my C++ code:
CDO::IMessagePtr iMsg(__uuidof(CDO::Message));
CDO::IConfigurationPtr iConf = iMsg->GetConfiguration();
CDO::FieldsPtr iFields;
_bstr_t empty("");
iConf->Load(CDO::cdoIIS,empty); // this string constant from import
iFields = iConf->Fields;
iFields->Item["https://schemas.microsoft.com/cdo/configuration/smtpserver"]->Value = _variant_t(szServer);
iFields->Item["https://schemas.microsoft.com/cdo/configuration/smtpserverport"]->Value = _variant_t(587);
iFields->Item["https//schemas.microsoft.com/cdo/configuration/sendusing"]->Value = 2;
iFields->Item["https//schemas.microsoft.com/cdo/configuration/smtpauthenticate"]->Value = _variant_t(1); // Basic
iFields->Item["https//schemas.microsoft.com/cdo/configuration/sendusername"]->Value = _variant_t(szUser);
iFields->Item["https//schemas.microsoft.com/cdo/configuration/sendpassword"]->Value = _variant_t(szPassword);
if(iUseSSLTLS == 2)
iFields->Item["https//schemas.microsoft.com/cdo/configuration/sendtls"]->Value = _variant_t(true);
else
iFields->Item["https//schemas.microsoft.com/cdo/configuration/smtpusessl"]->Value = _variant_t(true);
iFields->Update();
etc... etc...
If I use this code with smtp.gmail.com:
server: smtp.gmail.com,
port: 587,
sndtls = true,
account: my gmail account,
password:
I obtain the following response:
Code = 8004020e,
Code meaning = Impossibile modificare o eliminare un oggetto che è stato aggiunto utilizzando COM+ Admin SDK,
Source = (null),
Description = Indirizzo del mittente respinto dal server. Risposta del server: 530 5.7.0 Must issue a STARTTLS command first. y2sm3575389wme.12 - gsmtp,
(sorry ... part of the message is in Italian language, but take a look at the bold/italic one)
Obviously, if I configure Outlook 2010 using the same parameters, it works perfectly.
One more thing, if I use port 465 and SSL:
server: smtp.gmail.com,
port: 465,
smtpusessl= true,
account: my gmail account,
password:
the code works fine, but I need to configure 587 port and TLS.
I eventually tried smtpusessl and sendtls together, setting them true:
iFields->Item["https//schemas.microsoft.com/cdo/configuration/sendtls"]->Value = _variant_t(true);
iFields->Item["https//schemas.microsoft.com/cdo/configuration/smtpusessl"]->Value = _variant_t(true);
And I obtain the following error:
Code = 80040213
Code meaning = IDispatch error #19
Source = CDO.Message.1
Description = The transport failed to connect to the server.

Answer 1

After over 2 years, I found a solution, well ... not a solution, but now I know why it didn't work, e why it will never work. It seems there's a bug in CDO library: it can handle STARTTLS command on port 25, but it can't on port 587.
You can read more here:
https://social.technet.microsoft.com/Forums/en-US/37d00342-e5e9-4c8d-975d-44362332d426/bug-in-cdomessage-smtpserverport-587-fails?forum=ITCG
As I've just written above, it's a bug and I think Microsoft will never correct it. The recommendation for the future is to abandon CDO and use "Power shell" or third-party components.