A simple SMTP client library built in C++ that support authentication and secure connections (Opportunistic SSL/TLS and Forced SSL encryption).
Follow this link for a quick guide on how to build the SMTP client and integrate it in your application.
Follow these guides to build the library on Windows and Linux.
| Release | MD5 hash of smtpclient.dll |
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813e656a811af15891d4c1160a21dec9 |
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277b9c257decc619a6358de58b213928 |
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fb041c2e377d6e399853b1fd4f0f2396 |
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bb98d97a03451ff579226b0361c2a7ce |
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fc417d787a4533d3b6c99c1b5e852b5b |
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ffdd7f2adbf92b9a3dfd8bbf97c83008 |
See the section Releases for previous versions.
- Version 1.1.8:
- Some SMTP server send their list of supported extensions in multiple buffers like Zoho Mail. The EHLO command when in uncrypted mode, now supports receiving multiple buffers. In return, a delay of one second must be added for each segment sent by the SMTP server. For SMTP servers that send the list of supported extensions in a single segment like Gmail and Live, no additional delay is added for the EHLO command. This doesn't affect the other commands.
- Now when we send an email to multiple recipients (to or cc), the recipients appears as a single mail header instead of multiple headers. The old method was not RFC 5322 compliant.
- Version 1.1.7:
- Added support for the XOAUTH2 authentication method. This change has been made by rcosnita (https://github.com/rcosnita). Many thanks!
- Added a new flag in the different SMTP client classes to indicate whether we want to send emails in batch (getBatchMode/setBatchMode). In this mode the connection to an SMTP server will only be made once when the first email is sent and will remain open until the client instance is destroy.
- Added the authentication feature on the SMTPClient class.
- Added a new flag on the ForcedSecureSMTPClient and OpportunisticSecureSMTPClient to indicate whether we accept self signed certificate (getAcceptSelfSignedCert/setAcceptSelfSignedCert).
- Many more enhancements provided by ino-josh (https://github.com/ino-josh). Many thanks!
- Version 1.1.6: Added support in the attachment class for Content-ID. It will be really useful to uniquely identify and reference resources to embed in the message. This change has been made by hesa2020 (https://github.com/hesa2020). Many thanks!
The OpportunisticSecureSMTPClient should be your default choice for communicating with modern SMTP servers. The communication is usually done via port 587.
In this mode, the communication starts unencrypted, then the client will asked the server to provide the supported options and if the server supports encryption, the STARTTLS command will be sent. Negotiation will take place between the server and the client to find the most secure encryption to use for communication.
If the server does not support encryption, the communication will remain unencrypted and it will be logged in the communication log.
This client can be used for newest SMTP servers like Google Gmail, Microsoft Office 365 or good old uncrypted SMTP servers.
The ForcedSecureSMTPClient is useful to communicate with legacy systems which requires that the communication be encrypted from the initial connection. The communication is usually done via port 465.
The SmtpClient should be used to communicate with internal relay servers. It does not support encryption of communications. The communication is usually done via port 25.
You can consume objects in the library either using the C++ Interface (the jed_utils::cpp namespace) or using the Pure C Interface (the jed_utils namespace).
The Pure C Interface was designed primarily to maintain binary compatibility between major versions of the MSVC compiler toolsets. C++ binary compatibility between Visual Studio versions
To see some usage examples with Pure C Interface refer to the wiki Some examples with Pure C Interface
This problem has been resolved since 2015 so it is no longer an issue.
The C++ Interface should then be your default choice.
- Send a plaintext email via a secure server (opportunistic) -> SSL/TLS Port 587
- Send an html email to 2 recipients with an attachment via a secure server
- Send a plaintext email via a secure server (forced) -> SSL/TLS Port 465
#include "cpp/opportunisticsecuresmtpclient.hpp"
#include "cpp/plaintextmessage.hpp"
#include <iostream>
#include <stdexcept>
using namespace jed_utils::cpp;
int main() {
OpportunisticSecureSMTPClient client("<your smtp server address>", 587);
client.setCredentials(Credential("[email protected]", "mypassword"));
try {
PlaintextMessage msg(MessageAddress("[email protected]", "Test Address Display"),
{ MessageAddress("[email protected]", "Another Address display") },
"This is a test (Subject)",
"Hello\nHow are you?");
int err_no = client.sendMail(msg);
if (err_no != 0) {
std::cerr << client.getCommunicationLog() << '\n';
std::string errorMessage = client.getErrorMessage(err_no);
std::cerr << "An error occurred: " << errorMessage
<< " (error no: " << err_no << ")" << '\n';
return 1;
}
std::cout << client.getCommunicationLog() << '\n';
std::cout << "Operation completed!" << std::endl;
}
catch (std::invalid_argument &err) {
std::cerr << err.what() << std::endl;
}
return 0;
}You will need to include cpp/htmlmessage.hpp
OpportunisticSecureSMTPClient client("<your smtp server address>", 587);
client.setCredentials(Credential("[email protected]", "mypassword"));
const MessageAddress from("[email protected]", "Test Address Display");
const auto to = { MessageAddress("[email protected]") };
const auto subject = "This is a test (Subject)";
const auto body = "<html><body><h1>Hello,</h1><br/><br/>How are you?</body></html>";
const auto cc = { MessageAddress("[email protected]") };
const std::vector<MessageAddress> bcc = {};
const auto attachment = { Attachment("C:\\Temp\\test.png", "test image.png") };
HTMLMessage msg(from, to, subject, body, cc, bcc, attachment);
client.sendMail(msg);You will need to include cpp/forcedsecuresmtpclient.hpp
ForcedSecureSMTPClient client("<your smtp server address>", 465);
client.setCredentials(Credential("[email protected]", "mypassword"));
PlaintextMessage msg(MessageAddress("[email protected]", "Test Address Display"),
{ MessageAddress("[email protected]", "Another Address display") },
"This is a test (Subject)",
"Hello\nHow are you?");
client.sendMail(msg);
}You will need to include cpp/htmlmessage.hpp
OpportunisticSecureSMTPClient client("<your smtp server address>", 587);
client.setCredentials(Credential("[email protected]", "mypassword"));
const MessageAddress from("[email protected]", "Test Address Display");
const auto to = { MessageAddress("[email protected]") };
const auto subject = "This is a test (Subject)";
const auto body = "<html><body><img src='cid:[email protected]' /></body></html>";
const auto cc = { MessageAddress("[email protected]") };
const std::vector<MessageAddress> bcc = {};
const auto attachment = { Attachment("C:\\Temp\\test.png", "test image.png", "[email protected]") };
HTMLMessage msg(from, to, subject, body, cc, bcc, attachment);
client.sendMail(msg);The library keeps each exchange between the client and the server in the communication log for easy diagnosis in the event of a communication problem.
Here's is an example communication log of a successful email send :
c: Trying to connect to smtp.gmail.com on port 587
s: 220 smtp.gmail.com ESMTP v2-20020a05620a440200b006fed2788751sm17411101qkp.76 - gsmtp
c: Connected!
c: ehlo localhost\r\n
s: 250-smtp.gmail.com at your service, [129.222.207.110]
250-SIZE 35882577
250-8BITMIME
250-STARTTLS
250-ENHANCEDSTATUSCODES
250-PIPELINING
250-CHUNKING
250 SMTPUTF8
c: Info: STARTTLS is available by the server, the communication will be encrypted.
c: STARTTLS\r\n
s: 220 2.0.0 Ready to start TLS
c: <Start TLS negotiation>
c & s: <Negotiate a TLS session>
c & s: <Check result of negotiation>
c: TLS session ready!
c: Contacting the server again but via the secure channel...
c: ehlo localhost\r\n
s: 250-smtp.gmail.com at your service, [129.222.207.110]
250-SIZE 35882577
250-8BITMIME
250-AUTH LOGIN PLAIN XOAUTH2 PLAIN-CLIENTTOKEN OAUTHBEARER XOAUTH
250-ENHANCEDSTATUSCODES
250-PIPELINING
250-CHUNKING
250 SMTPUTF8
c: AUTH PLAIN ***************\r\n
s: 235 2.7.0 Accepted
c: MAIL FROM: <Test Address Display [email protected]>\r\n
s: 250 2.1.0 OK v2-20020a05620a440200b006fed2788751sm17411101qkp.76 - gsmtp
c: RCPT TO: <youremailaddress@localhost>\r\n
s: 250 2.1.5 OK v2-20020a05620a440200b006fed2788751sm17411101qkp.76 - gsmtp
c: DATA\r\n
s: 354 Go ahead v2-20020a05620a440200b006fed2788751sm17411101qkp.76 - gsmtp
c: From: [email protected]\r\n
c: To: youremailaddress@localhost\r\n
c: Subject: This is a test (Subject)\r\n
c: Content-Type: multipart/mixed; boundary=sep\r\n\r\n
c: --sep\r\nContent-Type: text/html; charset=UTF-8\r\n\r\n<html><body><p>Body sample</p></body></html>\r\n
c: \r\n.\r\n
s: 250 2.0.0 OK 1672495787 v2-20020a05620a440200b006fed2788751sm17411101qkp.76 - gsmtp
c: QUIT\r\n
Operation completed!
We also provide a fully working example. See send-mail.cpp. Make sure you replace the username and password (access token) placeholders with correct values.
The example uses GMail smtp server with XOauth2 authentication mechanism.
For testing purposes, you can obtain an OAuth access token for you gmail account by using the OAuth 2.0 Playground. You can follow this procedure for more details: Obtaining an access token for your gmail account
See the classes documentation here
See LICENSE