Mail eh, could you be less specific. I presume you mean email. Sending, receiving, filtering, forwarding. Have a look at any of my favorites:
Mail::
::Address adpf? Manipulation of electronic mail addresses MARKOV
::Alias bdpO? Manipulate E-mail aliases and alias files ZELT
::Audit
RdpO? Toolkit for constructing mail filters SIMON
::Cap adpO? Parse mailcap files as specified in RFC 1524 MARKOV
::CheckUser Rdpfp Check email addresses for validity ILYAM
::Ezmlm bdpO? Object methods for ezmlm mailing lists GHALSE
::Field RdpO? Base class for handling mail header fields MARKOV
::Folder adpO? Base-class for mail folder handling KJOHNSON
::Freshmeat RdpOg Parses newsletters from http://freshmeat.net AFOXSON
::Header RdpO? Manipulate mail RFC822 compliant headers MARKOV
::Internet adpO? Functions for RFC822 address manipulations MARKOV
::MH adcr? MH mail interface MRG
::Mailer
adpO? Simple mail agent interface (see Mail::Send) MARKOV
::POP3Client RdpO? Support for clients of POP3 servers SDOWD
::Procmail Rdpf? Procmail-like facility for creating easy mai JV
::Send adpO?
Simple interface for sending mail MARKOV
::Sender
MdpOp socket() based mail with attachments, SMTP JENDA
::Sendmail Rdpfp Simple platform independent mailer MIVKOVIC
::UCEResponder i ? Spamfilter CHSTROSS
::Util adpf? Mail utilities (for by some Mail::* modules) MARKOV
::IMAPClient RdpO? An IMAP Client API DJKERNEN
::Box RmpOp Mail folder manager and MUA backend MARKOV
::Vmailmgr
bdpO? A Perl module to use Vmailmgr daemon MARTIN
::ListDetector bdpO? Mailing list message detector MSTEVENS
::PerlTix cmpO? Mail ticketing and transaction system JJARVINEN
::MboxParser RdpOp Read-only access to UNIX-mailboxes VPARSEVAL
::SpamAssassin bmpOa Mail::Audit spam detector plugin JMASON
::Verify
Rdpfb Attempt to verify an email address PETEF
::QmailRemote bdpOp send email using qmail-remote directly. IKEBE
::Sieve cdpOp RFC 3028 Mail Filtering BRONG
::VersionTracker bdpOg Parses newsletters from versiontracker.com AFOXSON
::Vacation adpOp perl implementation of vacation program RFOLEY
MIME::
::Base64 Rdhf? Encode/decode Base 64 (RFC 2045) GAAS
::QuotedPrint Rdpf? Encode/decode Quoted-Printable GAAS
::Decoder RdpO? OO interface for decoding MIME messages ERYQ
::Entity RdpO? An extracted and decoded MIME entity ERYQ
::Head RdpO? A parsed MIME header ERYQ
::Lite RdpO? Single module for composing simple MIME msgs ERYQ
::Parser RdpO? Parses streams to create MIME entities ERYQ
::Types
MdpOp Information and processing MIME types MARKOV
::Words Rdpf? Encode/decode RFC1522-escaped header strings ERYQ
Oh and last but not least who could forget
Net::SMTP adpf?
Interface to Simple Mail Transfer Protocol GBARR
tachyon
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