libtld is a library used to extract the TLD from a URI and to check email validity. This allows you to extract the exact domain name, sub-domains, and all the TLD (top level, second level, third level, etc.). The problem with TLDs is that you cannot know where the domain starts. Some domains can use one top-level domain, others use two, etc. However, it may be useful to know where the domain is to have the exact list of sub-domains. For example, if you want to force www. at the start of the domain name if no other sub-domains are specified, then you need to know exactly how many TLD are defined in a URI. The libtld offers one main function: tld(), which gives you a way to extract the TLD from any URI. The result is the offset where the TLD starts. This gives you enough information to extract everything else you need. For emails, the library is capable of parsing a string that represents a list of email addresses to be verified. The verification includes a check of the domain name and its TLD.
Inbucket is an email testing service. It accepts messages for any email address and makes them available to view via a Web interface. It allows Web developers, software engineers, and system administrators to quickly see the emailed output of their applications. No per-account setup is required. Mailboxes are created on the fly as mail is received for them, and no password is required to browse the content of the mailboxes.
stdnoj is a cross-platform C++ class library that includes classes for using portable strings, databases, SMTP, POP, NNTP, arrays, files, directories, logging, email, and sockets. While templates are used, no reliance upon STL or other (traditionally error-prone) technologies has been used, which increases portability between compilers.
MailChariot's only mission is to get your incoming email (for example from /var/spool/mail), filter it through a spam filter, and put it into a spam or ham mailbox. If you don't agree with the spam filter's decision, you can move it to the notspam or notham mailbox and MailChariot will mark the message as ham or spam respectively. This design is mail client agnostic. It is ideal for use on shared hosts where the provided spam filtering is not effective enough.
Twisted is an event-based framework for Internet applications. It includes a Web server, an SMTP/POP3 server, a telnet server, an SSH server, an IRC server, a DNS server, a generic client/server pair for remote object access (Perspective Broker), and APIs for creating new protocols. It supports integration with GTK+, GTK+ 2, Qt, Tkinter, wxPython, Mac OS X (PyObjC) and Win32 event loops. It also supports TCP, SSL and TLS, UDP, Unix sockets, multicast, and serial ports. Supported protocols include HTTP, FTP, SMTP, POP3, IMAP, TOC, OSCAR (AIM and ICQ), SSH, DNS, IRC, NNTP, Jabber, SOCKSv4, Telnet, SIP (for VoIP), and XML-RPC and SOAP using external packages. Most protocols are supported as both servers and clients.
qpsmtpd is a flexible smtpd daemon written in Perl. Apart from the core SMTP features, all functionality is implemented in small "extension plugins" using the easy-to-use object oriented plugin API. qpsmtpd was originally written as a drop-in qmail-smtpd replacement, but now it also includes an smtp forward and a postfix "backend".