The following is from the YAM Support web site and regards YAM 2.0.

The next major upgrade of YAM is currently under development. It will contain dozens of additions and improvements, therefore I call it YAM 2.0 instead of YAM 1.4.
I don't know the release date of YAM 2.0 yet, so please be patient.

Here is a list of the new features.

Copyright/startup window

[Screenshot]

• Built-in support for multiple users (like MultiYAM). Optionally, addressbooks and other config files can be shared
• During startup, the copyright window displays progress information

Main window

[Screenshot]

• All button and status images are user definable
• Attachments can be removed from the message
• Clicking the column titles in the message list will sort the messages
• Deleted messages are moved to a special 'Trash' folder
• Folders are listed in a listview including number of total and unread messages
• Folders containing unread messages are highlighted
• Functions also available through pulldown menus
• Graphical toolbar replaces text buttons
• Menu function to exchange mail (send queued and get new)
• Message size is now shown in bytes
• Messages can be redirected to another person (the original From header will be preserved)
• Messages with a high importance will be highlighted
• Removed default 'Archive' folder
• The status can be changed manually from read to unread and vice versa

Message window

[Screenshot]

• Attachments lists (SAVE, DISPLAY and PRINT buttons) now contain a Cancel option
• Double-clicking on a http or ftp URL starts user definable program like a web browser
• Double-click on a email address to a start a new message
• Copy any portion of the message to the clipboard
• Decryption of PGP encrypted messages
• Double-clicking an attachment will display it using the appropriate MIME viewer
• Message header is displayed in its own window
• Mutual exclude menus for header format
• Nested textstyles are now supported
• New message header format with better readability
• PGP signatures can be verified
• Possibility to disable textstyles
• Public PGP keys can be added to the public keyring
• Sends read confirmation to the sender if requested
• Up to 4 read windows can be opened at the same time
• User can choose between automatical word-wrap and horizontal scrolling

Transfer window

[Screenshot]

• Calculates remaining download/upload time
• Extensive filter statistics
• Select from a list which messages you want to download/delete from the POP3 server or import from a spool file
• YAM displays transfer speed in cps
• YAM now uses UIDL to avoid duplicate messages, but falls back to the Message-ID system of YAM 1.3.x if the server doesn't support UIDL

Address book; main window

[Screenshot]

• Address book can be printed (short or long format)
• Address book can be saved under a different name
• Address book can be sorted by alias, first name, last name, address or description
• Alternative address books can be loaded or appended
• Function to duplicate an entry
• Functions also available through pulldown menus
• Graphical toolbar replaces text buttons
• Single entries can be printed

Address book; single person entry

[Screenshot]

• A picture of the person can be displayed in the window
• Additional fields for person entries: street, city/ZIP, state/country, phone number, date of birth
• Up to 4 entry windows can be opened at the same time

Address book; mailinglist entry

[Screenshot]

• Additional fields for list entries: return address, mailinglist name

Write window; internal editor

[Screenshot]

• Dropping a file on the YAM Appicon will either insert it in the editor or append it as an attachment
• Graphical toolbar and pulldown menus for editor functions, including cut/copy/paste/undo and textstyles
• Internal editor allows spell checking (spells as you type); an external spell checker like AlphaSpell is required
• Message can be marked as HOLD to delay sending
• Message text can be saved
• Small menu to insert Emoticons into letter
• Text and clipboard contents can be inserted quoted or ROT13 encrypted
• Two write windows can be opened at the same time
• YAM now uses Texteditor.mcc by Allan Odgaard, a very fast MUI based editor which offers WYSIWYG of textstyles, ARexx port, configurable colors, cursor and frame
• BetterString gadgets (by Allan Odgaard): enhanced cursor navigation, clipboard support, filename completition, etc.
• Textclip library: marked text of any length can be saved in the library under a short name for later use.

Write window; security and other options

[Screenshot]

• Delivery confirmation using Return-Receipt-To
• Encrypt and/or sign a message using PGP
• Optionally turn of saving of sent messages
• Support for Importance header field
• User can select none, standard or alternative signatures

Find window (search for certain messages)

[Screenshot]

• Filters and search function for address fields can use a file that contains many patterns ("killfile")
• Filters can be easily created based on the current search options, and vice versa
• Selection of multiple messages by pattern

Configuration; First steps

[Screenshot]

• POP3 password will be requested if there's no entry in the configuration
• Timezone for date header is now settable in the configuration and defaults to Locale prefs

Configuration; TCP/IP settings

[Screenshot]

• APOP login is now supported
• Option to send messages in 8bit without MIME encoding
• Option to specify SMTP domain name for HELO command
• Up to 16 POP3 servers can be checked in one step

Configuration; Receive mail

[Screenshot]

• On new mail, YAM displays a requester and/or plays a sound (OS 3.x only) and/or executes a command
• Optionally, YAM marks new messages as unread before getting new mail

Configuration; Folders

[Screenshot]

• Folders can be automatically compressed using XPK
• Folders can be protected using a password (XPK encryption)
• Mailing list support: if To: field matches a folder-specific pattern, the return address is taken from the config
• Max.age option: Messages that are older than a certain age are automatically deleted
• Messages can be sorted by increasing or decreasing message date, dated received, sender, recipient, subject, status or size
• Two sort keys for each folder

Configuration; Filters

[Screenshot]

• 'Apply to new' and 'Apply on request' can be set individually for each filter
• "Remote filters" can be used to delete or skip messages on the POP3 server without downloading
• Additional searchable fields: CC, Reply-To, Date, user-configurable field or size
• Available comparison operators: equal, not equal, bigger than, smaller than
• Filters can search for a certain status
• Filters can search the whole message, header only or body only
• Matching messages can be redirected, forwarded, replied (using an existing message file), moved or deleted, they can also start an ARexx script
• Multiple actions are allowed for each filter
• Substring search option obsoletes #? pattern

Configuration; Read options

[Screenshot]

• Charset translation
• Headers to show in 'short' format can now be configured
• Option to display sender information (from the address book) in the header, including portrait

Configuration; Write options

[Screenshot]

• 'Welcome' and 'greetings' phrases
• Charset translation (includes some example translation tables like AmigaPL to ISO-Latin2)
• Editor font, tabsize, wordwrap column and cursor type are configurable
• Editor option to automatically insert line breaks
• Optionally, the external editor will be launched immediately
• Support for additional headers

Configuration; Reply/forward options

[Screenshot]

• Alternative reply intro is used if the recipient's address matches a given pattern
• Enhanced reply subject generation (Re[2]:, Re[3]:, etc...)
• New variable for quote text: first and last initial
• New variable for reply/forward phrases: message id
• New variables for forward phrases: name/first name/address of original recipient
• Optional warning if Reply-To and From addresses are not equal

Configuration; Signatures and taglines

[Screenshot]

• Random tagline support, location and format of cookies are configurable

Configuration; GUI layout

[Screenshot]

• Toolbar modes: image only, text only, mixed
• User can set width and contents of each column for the folder, message and address book lists

Configuration; PGP, remailer, logfiles

[Screenshot]

• Anonymize a message using a re-mailer service
• Generation of normal or verbose logfiles
• Optionally a new logfile is created for every month

Configuration; Start/quit options

[Screenshot]

• Quit options: send queued mail, delete old mail, removed deleted mail
• Startup options: load all folders, mark new mail as unread, send queued mail, download new mail
• YAM reminds you on your friends' birthdays (using the data from the address book)

Configuration; Miscellaneous settings, part 1

[Screenshot]

• Option to set default directory for files to attach

Configuration; Miscellaneous settings, part 2

[Screenshot]

• Read/process confirmation using Message Disposition Notification (MDN): get a message when the recipient reads, forwards or deletes your message
• MDNs are sent automatically or after your confirmation

Configuration; ARexx macros

[Screenshot]

• 10 ARexx hooks that will be called on certain events
• An Arexx script can optionally run asynchronously and/or open a console window
• Contents of ARexx menu can be defined in the configuration window
• MUI Arexx port has been disabled, YAM now uses ARexxBox code for a style- guide conformant ARexx interface
• New FOLDERINFO, MAILINFO and CONFIGINFO commands return internal information in a stem variable

Things that WON'T be in YAM 2.0

• Hierarchical folder structure
• INet 225 support (working bsdsocket.library emulation for INet 225 is available)
• Inline decoding of attached pictures and sounds
• Newsgroups support
• Support for IMAP 2/4 protocol

Find window (search for certain messages)

• Filters and search function for address fields can use a file that contains many patterns ("killfile")
• Filters can be easily created based on the current search options, and vice versa
• Selection of multiple messages by pattern

Configuration; First steps

• POP3 password will be requested if there's no entry in the configuration
• Timezone for date header is now settable in the configuration and defaults to Locale prefs

Configuration; TCP/IP settings

• APOP login is now supported
• Option to send messages in 8bit without MIME encoding
• Option to specify SMTP domain name for HELO command
• Up to 16 POP3 servers can be checked in one step

Configuration; Receive mail

• On new mail, YAM displays a requester and/or plays a sound (OS 3.x only) and/or executes a command
• Optionally, YAM marks new messages as unread before getting new mail

Configuration; Folders

• Folders can be automatically compressed using XPK
• Folders can be protected using a password (XPK encryption)
• Mailing list support: if To: field matches a folder-specific pattern, the return address is taken from the config
• Max.age option: Messages that are older than a certain age are automatically deleted
• Messages can be sorted by increasing or decreasing message date, dated received, sender, recipient, subject, status or size
• Two sort keys for each folder

Configuration; Filters

• 'Apply to new' and 'Apply on request' can be set individually for each filter
• "Remote filters" can be used to delete or skip messages on the POP3 server without downloading
• Additional searchable fields: CC, Reply-To, Date, user-configurable field or size
• Available comparison operators: equal, not equal, bigger than, smaller than
• Filters can search for a certain status
• Filters can search the whole message, header only or body only
• Matching messages can be redirected, forwarded, replied (using an existing message file), moved or deleted, they can also start an ARexx script
• Multiple actions are allowed for each filter
• Substring search option obsoletes #? pattern

Configuration; Read options

• Charset translation
• Headers to show in 'short' format can now be configured
• Option to display sender information (from the address book) in the header, including portrait

Configuration; Write options

• 'Welcome' and 'greetings' phrases
• Charset translation (includes some example translation tables like AmigaPL to ISO-Latin2)
• Editor font, tabsize, wordwrap column and cursor type are configurable
• Editor option to automatically insert line breaks
• Optionally, the external editor will be launched immediately
• Support for additional headers

Configuration; Reply/forward options

• Alternative reply intro is used if the recipient's address matches a given pattern
• Enhanced reply subject generation (Re[2]:, Re[3]:, etc...)
• New variable for quote text: first and last initial
• New variable for reply/forward phrases: message id
• New variables for forward phrases: name/first name/address of original recipient
• Optional warning if Reply-To and From addresses are not equal

Configuration; Signatures and taglines

• Random tagline support, location and format of cookies are configurable

Configuration; GUI layout

• Toolbar modes: image only, text only, mixed
• User can set width and contents of each column for the folder, message and address book lists

Configuration; PGP, remailer, logfiles

• Anonymize a message using a re-mailer service
• Generation of normal or verbose logfiles
• Optionally a new logfile is created for every month

Configuration; Start/quit options

• Quit options: send queued mail, delete old mail, removed deleted mail
• Startup options: load all folders, mark new mail as unread, send queued mail, download new mail
• YAM reminds you on your friends' birthdays (using the data from the address book)

Configuration; Miscellaneous settings, part 1

• Option to set default directory for files to attach

Configuration; Miscellaneous settings, part 2

• Read/process confirmation using Message Disposition Notification (MDN): get a message when the recipient reads, forwards or deletes your message
• MDNs are sent automatically or after your confirmation

Configuration; ARexx macros

• 10 ARexx hooks that will be called on certain events
• An Arexx script can optionally run asynchronously and/or open a console window
• Contents of ARexx menu can be defined in the configuration window
• MUI Arexx port has been disabled, YAM now uses ARexxBox code for a style- guide conformant ARexx interface
• New FOLDERINFO, MAILINFO and CONFIGINFO commands return internal information in a stem variable

Things that WON'T be in YAM 2.0

• Hierarchical folder structure
• INet 225 support (working bsdsocket.library emulation for INet 225 is available)
• Inline decoding of attached pictures and sounds
• Newsgroups support
• Support for IMAP 2/4 protocol

As soon as YAM 2.0 is released, I will inform you.