Mailers are clever bits of software that transport files across the Telephone Lines. They dial out, and connect to other mailers, exchange their files, then disconnect. Some mailers offer advanced features such as dynamic mail routing, and scheduled events. They can also pass BBS callers onto the BBS Software. The more advanced mailers are usually quite difficult to setup, so bear that in mind when selecting your preferred mailer.
Here are a number of Specific FTN Mailers. The OS icons beside the names of the mailers indicate they have native OS platforms in that software.
FrontDoor.
Frontdoor is one of the most popular mailers around. The dos mailer comes with message editor, and is made in Sweden
Frontdoor APX is a fully integrated
pointing system for FTN networks available for Windows or Dos. It
includes a message editor, mailer, and tosser
URL: http://www.defsol.se/
T-Mail
-Mail is an electronic mail program,
designed for use in FidoNet Technology Networks, that is,
networks which are based upon FidoNet standards. Nodes of these
networks exchange information by means of the switched telephone
network using modems.T-Mail is designed to handle the automatic
exchange of information between FTN-nodes. T-Mail implements
developed and accepted FidoNet Technical Standards (FTS) such as
(EMSI/YooHoo/ZedZap/Janus/Hydra/WaZOO). T-Mail will handle the
receipt and transmission of mail, the preparation of mail, and
the execution of external programs by remote command. Fax
operations (with a fax capable modem) and a voice answer-back (voice
capable modem) are possible with the commercial version.
URL: T-Mail Web Site
FTP: T-Mail FTP Site
McMail
McMail is a FTN-compatible Mailer for DOS, with a Binkleystyle Outbound, Internal Netmailrouting, Outboundmanager Hydra Chat protocol with Chat, Costcalculation & Request-Processor Interface. It supports up to 99 lines with Visual LineControl, FAX and IEMSI capabilities and much more...
The unofficial support
site also contains lots of 3rd party utilities to help make the
most of McMail
URL: http://www.fidonet.dnet.co.uk/mcmail/
Portal Of Power
Portal Of Power (PoP) is another
McMail type Mailer, and very similar. Development is finished
afaik
URL:
BinkleyTerm
BinkleyTerm is a freely available FidoNet compatible electronic mail interface and dumb terminal package. This means it's a program for receiving and sending mail and files within FidoNet or other Fido Technology Networks.
After publishing the source code of BinkleyTerm v2.60 for free again, a lot of people around the world added their changes, additions and fixes to this version. Only Thomas Waldmann tried to launch a team for coordinating this. The BinkleyTerm modified by this team (The BT-XE Team) is called BinkleyTerm XE or short BT-XE. XE means eXtended Edition (EE was already used by Michael Bünter for his modified version of BinkleyTerm v2.50).
BinkleyTerm XE supports all common protocols used within the FidoNet like WaZoo, EMSI, ZedZap, Janus, Hydra and xHydra.
URL: BlinkyTerm Web Site
Xenia
Xenia is an advanced
FidoNet-technology compatible mailer and message reader/editor
designed by Arjen G. Lentz of Lentz Software Development. It is
available in both DOS and OS/2 versions - fully functional
evaluation package.
URL: Lentz Software Development Web Site
Beemail
Beemail is a Windows GUI
FidoNet E-mail system which can be used as a front-end mailer for
any Windows or DOS based BBS supporting front-end mailers.
URL: BeeMail Web Site
Argus 
Argus is a comprehensive FTN Mailer
designed to work as a multi-line system using two widely used
data exchange transports - Dial-up networking and TCP/IP -
simultaneously. Argus interacts with remote systems using
protocols and technology standards described in this chapter.
Because Argus is built on FTN Technology (FidoNet Technology
Network), it supports standards and proposals developed by FTN
committee, common standards of FTN mail system functions are also
supported by Argus.
URL: ArguS Homepage