mailio

mailio is a cross platform C++ library for MIME format and SMTP, POP3 and IMAP protocols. It is based on standard C++ 17 and Boost library.

Examples

To send a mail, one has to create message object and set it's attributes as author, recipient, subject and so on. Then, an SMTP connection is created by constructing smtp (or smtps) class. The message is sent over the connection:

message msg;
msg.from(mail_address("mailio library", "mailio@gmail.com"));
msg.add_recipient(mail_address("mailio library", "mailio@gmail.com"));
msg.subject("smtps simple message");
msg.content("Hello, World!");

smtps conn("smtp.gmail.com", 587);
conn.authenticate("mailio@gmail.com", "mailiopass", smtps::auth_method_t::START_TLS);
conn.submit(msg);

To receive a mail, message object is created to store the received message. Mail can be received over POP3 or IMAP, depending of mail server setup. If POP3 is used, then instance of pop3 (or pop3s) class is created and message is fetched:

pop3s conn("pop.mail.yahoo.com", 995);
conn.authenticate("mailio@yahoo.com", "mailiopass", pop3s::auth_method_t::LOGIN);
message msg;
conn.fetch(1, msg);

Receiving a message over IMAP is analogous. Since IMAP recognizes folders, then one has to be specified, like inbox:

imaps conn("imap.gmail.com", 993);
conn.authenticate("mailio@gmail.com", "mailiopass", imap::auth_method_t::LOGIN);
message msg;
conn.fetch("inbox", 1, msg);

More advanced features are shown in examples directory, see below how to compile them.

Note for Gmail users: if 2FA is turned on, then instead of the primary password, the application password must be used. Follow Gmail instructions to add mailio as trusted application and use the generated password for all three protocols.

Note for Zoho users: if 2FA is turned on, then instead of the primary password, the application password must be used. Follow Zoho instructions to add mailio as trusted application and use the generated password for all three protocols.

Requirements

Mailio library is supposed to work on all platforms supporting C++ 17 compiler, recent Boost libraries and CMake build tool.

For Linux the following configuration is tested:

gcc 8.3.0.
Boost 1.66 with Regex, Date Time available.
POSIX Threads, OpenSSL and Crypto libraries available on the system.
CMake 3.11

For MacOS the following configuration is tested:

Apple LLVM 9.0.0.
Boost 1.66.
OpenSSL 1.0.2n available on the system.
CMake 3.10.

For Microsoft Windows the following configuration is tested:

Windows 10.
Visual Studio 2015 Community Edition.
Boost 1.66.
OpenSSL 1.0.2n available on the system.
CMake 3.11.

Setup

Ensure that OpenSSL, Boost and CMake are in the path. If they are not in the path, one could set environment variables OPENSSL_ROOT_DIR and BOOST_ROOT to their respective paths. Boost must be built with OpenSSL support. If it cannot be found in the path, set the path explicitly via library-path and include parameters of b2 script (after bootstrap finishes).

Linux, MacOS

From the terminal go into the directory where the library is downloaded to, and execute:

mkdir build
cd ./build
cmake ..
make

Both static and dynamic libraries should be built in the build directory. If one wants to specify non-default installation directory say /opt/mailio, then the last two steps should be:

cmake -DCMAKE_INSTALL_PREFIX=/opt/mailio ..
make install

Other available options are MAILIO_BUILD_SHARED_LIBRARY (by default is on, if turned off then the static library is built), MAILIO_BUILD_DOCUMENTATION (if Doxygen documentation is generated, by default is on) and MAILIO_BUILD_EXAMPLES (if examples are built, by default is on).

Microsoft Windows

From the command prompt go into the directory where the library is downloaded, and execute:

mkdir build
cd .\build
cmake ..

A solution file will be built, open it from Visual Studio and build the project.

Features

Recursive formatter and parser of the MIME message.
MIME message recognizes the most common headers like subject, recipients, content type and so on.
Encodings that are supported for the message body: Seven bit, Eight bit, Binary, Base64 and Quoted Printable.
Subject, attachment and name part of the mail address can be in ASCII or UTF-8 format.
All media types are recognized, including MIME message embedded within another message.
MIME message has configurable line length policy and strict mode for parsing.
SMTP implementation with message sending. Both plain and SSL (including START TLS) versions are available.
POP3 implementation with message receiving and removal, getting mailbox statistics. Both plain and SSL (including START TLS) versions are available.
IMAP implementation with message receiving, removal and search, getting mailbox statistics, managing folders. Both plain and SSL (including START TLS) versions are available.

Issues

The library is tested on valid mail servers, so probably there are negative test scenarios that are not covered by the code. In case you find one, please contact me. Here is a list of issues known so far and planned to be fixed in the future.

Non-ASCII subject is assumed to be UTF-8.
Non-ASCII attachment name is assumed to be UTF-8.
Header attribute cannot contain space between name and value.
SSL certificate is not verified.

Roadmap

version 0.8.0 (Q4/2016): More advanced test scenarios, more examples.
version 0.9.0 (Q4/2016): Binary content transfer encoding, strict mode for codec parsers.
version 0.10.0 (Q2/2017): Strict mode for message parser.
version 0.11.0 (Q2/2017): Q codec to support non-ASCII message subjects.
version 0.12.0 (Q3/2017): Non-ASCII name part of a mail address.
version 0.13.0 (Q4/2017): UTF-8 filename of an attachment.
version 0.14.0 (Q4/2017): Mail content is sent with attachments as another MIME part.
version 0.15.0 (Q1/2018): Line policy applied to the header. Clang/MacOS build support in Makefile.
version 0.16.0 (Q2/2018): Cmake scripts tested on Linux, MacOS and Windows. Sender header added.
version 0.17.0 (Q3/2018): Timeouts for I/O operations. Fetching only message header with IMAP.
version 0.18.0 (Q1/2019): Fixes of IMAP parser. Managing folders in IMAP.
version 0.19.0 (Q3/2019): IMAP searching, fetching messages by UIDs.

Contributors

Trevor Mellon: CMake build scripts.
Kira Backes: Fix for correct default message date.
sledgehammer_999: Replacement of Boost random function with the standard one.
Paul Tsouchlos: Modernizing build scripts.
Anton Zhvakin: Replacement of deprecated Boost Asio entities.
terminator356: IMAP searching, fetching messages by UIDs.

Contact

In case you find a bug, please drop me a mail to contact (at) alepho.com. Since this is my side project, I'll do my best to be responsive.

nicraMarcin / mailio