Not included in initial defaults registry. defaults read com.apple.mail UserHeaders
defaults write com.apple.mail UserHeaders '{"Disposition-Notification-To" = "Name "; }'
replacing Name with your name and email@address with your email address. The complete line could read "defaults write com.apple.mail UserHeaders '{"Disposition-Notification-To" = "Heinz Tschabitscher "; }'", for example.

from about.com

GUIDs have been replaced by ⨌ 

defaults read com.apple.mail UserHeaders


{   ABDefaultSelectedMember = "⨌:ABPerson";
    ABMainWindowViewMode = 0;
    AccountsVersion = 11;
    ActiveEditors =     (
                {
            EditorClassName = MailDocumentEditor;
            SelectedMessageIDs =             ( ⨌1@Real-World-Systems.com>");
            StorePath = "~/Library/Mail/POP-dgerman@real-world-systems.com@mail.real-world-systems.com/Drafts.mbox";
            WindowFrame = "364 52 916 726 0 0 1280 778 "; },
                {
            EditorClassName = MailDocumentEditor;
            SelectedMessageIDs =             ( ⨌2@real-world-systems.com>");
            StorePath = "~/Library/Mail/POP-dgerman@real-world-systems.com@mail.real-world-systems.com/Drafts.mbox";
            WindowFrame = "184 52 916 726 0 0 1280 778 "; }
    );

ActiveSingleViewers = (); ActiveViewers = ( { DisplayInThreadedMode = no; SearchPopupTag = 4; SearchSortDescending = 1; SearchSortOrder = rank; SelectedMailboxes = ( "~/Library/Mail/POP-realger1@real-world-systems.com/INBOX.mbox"); SelectedMessageIDs = { "///MessageList///" = ( 1251); }; ShowDeletedMessages = 0; SortOrder = "received-date"; SortedDescending = 1; ToolbarIsHidden = 0; ViewerNumber = 1; } );

AddInvitationsToICalAutomatically = 0; AddressDisplayMode = 4; AutoFetch = 1; CalSuccessfulLaunchTimestampPreferenceKey = "2.85625e+08"; CheckedForOldLSMMapFile = 1; CurrentTransferMailboxPath = "~/Library/Mail/Mailboxes/ISP.mbox"; DateCellWidthCache = { DateCellCacheVersion = "B Version"; DateCellFormats = ( "MMMM d, yyyy' '", "MMM d, yyyy' '", "M/d/yy' '", "MMMM d, yyyy", "MMM d, yyyy", "M/d/yy", "Yesterday ", "Today ", Yesterday, Today); Font = LucidaGrande; FontSize = 12; Language = en; Widths = ( "177.85546875", "138.861328125", "116.82421875", "119.14453125", "80.150390625", "58.11328125", "117.169921875", "95.765625", "56.8125", "35.408203125"); }; DeliveryAccounts = ( { AccountName = RWS; AccountType = SMTPAccount; Hostname = "real-world-systems.com"; IsSyncable = 1; MaxMessageBytes = 52428800; SSLEnabled = YES; SecurityLayerType = 2; ShouldUseAuthentication = NO; UseDefaultPorts = YES; uniqueId = "⨌"; } ); DraftsViewerAttributes = { DisplayInThreadedMode = no; SearchSortDescending = YES; SearchSortOrder = rank; SortOrder = "last-saved-date"; SortedDescending = NO; }; HasSetupIndexingDefaults = 1; IMAPServerPrefixesMirrorFilesystem = 1; InboxViewerAttributes = { DisplayInThreadedMode = no; SearchSortDescending = YES; SearchSortOrder = rank; SortOrder = "received-date"; SortedDescending = YES; }; IndexJunk = 1; IndexTrash = 1; JunkMailBehavior = 2; JunkViewerAttributes = { DisplayInThreadedMode = no; SearchSortDescending = YES; SearchSortOrder = rank; SortOrder = "received-date"; SortedDescending = NO; }; LastAttachedDir = "/Volumes/DATA-1/documents/DGerman/JobSearch"; Locations = ( { AccountDefaults = { }; Identities = { "192.168.1" = ( "germans.Germans", "doubleClick.net"); }; } ); MailAccounts = ( { AccountPath = "~/Library/Mail/RSS"; AccountType = RSSAccount; DraftsMailboxName = Drafts; JunkMailboxName = Junk; SentMessagesMailboxName = "Sent Messages"; uniqueId = "⨌"; }, { AccountPath = "~/Library/Mail/Mailboxes"; AccountType = LocalAccount; DraftsMailboxName = Drafts; IsSyncable = 1; JunkMailboxName = Junk; NotesMailboxName = Notes; SentMessagesMailboxName = "Sent Messages"; TrashMailboxName = "Deleted Messages"; uniqueId = "⨌"; }, { AccountName = dgerman; AccountPath = "~/Library/Mail/POP-dgerman@real-world-systems.com@mail.real-world-systems.com"; AccountType = POPAccount; BigMessageWarningSize = "-1"; DeleteMessagesOnServerInterval = 7; DeletionPolicy = Never; DraftsMailboxName = Drafts; EmailAddresses = ( "dgerman@real-world-systems.com"); FullUserName = "Dennis German"; Hostname = "mail.real-world-systems.com"; IsSyncable = 1; JunkMailboxName = Junk; PortNumber = 995; SMTPIdentifier = "real-world-systems.com"; SSLEnabled = YES; SecurityLayerType = 3; SentMessagesMailboxName = "Sent Messages"; TrashMailboxName = "Deleted Messages"; Username = "dgerman@real-world-systems.com"; uniqueId = "51e38965-8866-4f10-912f-eccb59842497"; }, { AccountName = RWS; AccountPath = "~/Library/Mail/POP-realger1@real-world-systems.com"; AccountType = POPAccount; BigMessageWarningSize = "-1"; DeleteMessagesOnServerInterval = 7; DeletionPolicy = Never; DraftsMailboxName = Drafts; EmailAddresses = ( "dgerman@real-world-systems.com"); FullUserName = RWS; Hostname = "real-world-systems.com"; IsSyncable = 1; JunkMailboxName = Junk; LockDeliveryAccount = NO; PortNumber = 995; SMTPIdentifier = "real-world-systems.com"; SSLEnabled = YES; SecurityLayerType = 3; SentMessagesMailboxName = "Sent Messages"; TrashMailboxName = "Deleted Messages"; Username = realger1; uniqueId = "23c46b45-d6a0-4257-836b-9aea22d15d1a"; } ); MailSections = ( MailboxesSection, RemindersSection, "feed:///", "local:///", "pop://dgerman%40real-world-systems.com@mail.real-world-systems.com/", "pop://realger1@real-world-systems.com/" ); MailShowNotes = 1; MailShowToDos = 0; MailSound = "/System/Library/Sounds/Glass.aiff"; MailVisibleSections = ( MailboxesSection, RemindersSection, "feed:///", "local:///" ); NSFontPanelAttributes = "1, 4"; NSNavBrowserPreferedColumnContentWidth = 186; NSNavLastCurrentDirectory = "/Volumes/DATA-1/documents/DGerman/JobSearch"; NSNavLastRootDirectory = "/Volumes/DATA-1"; NSNavPanelExpandedSizeForOpenMode = "{1019, 509}"; "NSOutlineView Items Main Window Mailbox List 0" = ( "~/Library/Mail/Mailboxes", "~/Library/Mail/Mailboxes/10Q1.mbox", MailboxesSection, "~/Library/Mail/RSS" ); "NSOutlineView Items Main Window Mailbox List 1" = ( "~/Library/Mail/Mailboxes", "~/Library/Mail/RSS", Inbox, MailboxesSection, "~/Library/Mail/Mailboxes/10Q1.mbox", RemindersSection); NSPreferencesContentSize = "{550, 520}"; NSPreferencesSelectedIndex = 6; "NSSplitView Subview Frames ABPeoplePickerView-People Picker" = ( "0.000000, 0.000000, 192.000000, 174.000000, NO", "193., 0., 267., 174., NO"); "NSSplitView Subview Frames Main Window 0" = ( "0., 0., 137., 565., NO", "138., 0., 786., 565., NO"); "NSSplitView Subview Frames Main Window 1" = ( "0., 0., 137., 673., NO", "138., 0., 988., 673., NO"); "NSSplitView Subview Frames Main Window Preview Pane 0" = ( "0., 0., 786., 173., NO", "0., 183., 786., 382., NO"); "NSSplitView Subview Frames Main Window Preview Pane 1" = ( "0., 0., 988., 231., NO", "0., 241., 988., 432., NO"); "NSTableView Columns ABLDAPTableView" = ( <040b7374 7265616d 74797065 6481e803 84014084 8484084e 53537472 696e6701 8484084e 534f626a 65637400 8584012b 06616374 69766586>, 40, <040b7374 7265616d 74797065 6481e803 84014084 8484084e 53537472 696e6701 8484084e 534f626a 65637400 8584012b 06736572 76657286>, 141, <040b7374 7265616d 74797065 6481e803 84014084 8484084e 53537472 696e6701 8484084e 534f626a 65637400 8584012b 04686f73 7486>, 175 ); "NSTableView Hidden Columns ABLDAPTableView" = (); "NSTableView Sort Ordering ABLDAPTableView" = (); "NSToolbar Configuration NSPreferences" = { "TB Display Mode" = 1; "TB Icon Size Mode" = 1; "TB Is Shown" = 0; "TB Item Identifiers" = ( General, Accounts, RSS, "Junk Mail", "Fonts & Colors", Viewing, Composing, Signatures, Rules); "TB Size Mode" = 1; "TB Visibility Priority Values" = { }; }; "NSWindow Frame Address Book" = "112 276 460 227 0 0 1280 778 "; "NSWindow Frame Compose Window" = "184 52 916 726 0 0 1280 778 "; "NSWindow Frame Connection Doctor" = "49 313 1216 465 0 0 1280 778 "; "NSWindow Frame Main Window 0" = "242 178 924 586 0 0 1280 778 "; "NSWindow Frame Main Window 1" = "99 84 1126 694 0 0 1280 778 "; "NSWindow Frame Note Window" = "140 373 324 382 0 0 1280 778 "; "NSWindow Frame Preferences" = "42 100 593 390 0 0 1280 778 "; "NSWindow Frame Torn Off Window" = "171 52 916 726 0 0 1280 778 "; NumberOfMessagesMarkedAsNotJunk = 10; OutboxMailboxPath = "~/Library/Mail/Mailboxes/Outbox.mbox"; OutboxViewerAttributes = { DisplayInThreadedMode = no; SearchSortDescending = YES; SearchSortOrder = rank; SortOrder = "sent-date"; SortedDescending = NO; }; PollTime = 1; RSSDefaultFeedsVersion = 1; SentMessagesViewerAttributes = { DisplayInThreadedMode = no; SearchSortDescending = YES; SearchSortOrder = rank; SortOrder = "sent-date"; SortedDescending = YES; }; ShouldShowUnreadMessagesInBold = 1; ShowActivity = 0; ShowActivityViewer = 1; ShowAddressBook = 0; ShowPresence = 1; SignatureSelectionMethods = { "51e38965-8866-4f10-912f-eccb59842497" = SelectedOnly; }; SignaturesSelected = { }; SpellCheckingBehavior = InlineSpellCheckingEnabled; TableColumns = { drafts = { 0 = { automaticInsertionOkay = 0; automaticInsertionWhileSearchingOkay = 0; columnIdentifier = 0; isVisible = 0; position = 1; positionWhileSearching = 1; widthWithLocation = 20; widthWithRank = 20; widthWithRankAndLocation = 20; widthWithThreading = 0; widthWithThreadingWithLocation = 0; widthWithoutRankAndLocation = 20; widthWithoutThreading = 20; widthWithoutThreadingWithLocation = 20; }; 10 = { automaticInsertionOkay = 1; automaticInsertionWhileSearchingOkay = 0; columnIdentifier = 10; isVisible = 0; position = "-1"; positionWhileSearching = "-1"; widthWithLocation = 72; widthWithRank = 72; widthWithRankAndLocation = 72; widthWithThreading = 72; widthWithThreadingWithLocation = 72; widthWithoutRankAndLocation = 72; widthWithoutThreading = 72; widthWithoutThreadingWithLocation = 72; }; 11 = { automaticInsertionOkay = 1; automaticInsertionWhileSearchingOkay = 1; columnIdentifier = 11; isVisible = 0; position = 6; positionWhileSearching = "-1"; widthWithLocation = 100; widthWithRank = 100; widthWithRankAndLocation = 100; widthWithThreading = 100; widthWithThreadingWithLocation = 100; widthWithoutRankAndLocation = 100; widthWithoutThreading = 100; widthWithoutThreadingWithLocation = 100; }; 13 = { automaticInsertionOkay = 0; automaticInsertionWhileSearchingOkay = 0; columnIdentifier = 13; isVisible = 1; position = 1; positionWhileSearching = 2; widthWithLocation = 20; widthWithRank = 20; widthWithRankAndLocation = 20; widthWithThreading = 20; widthWithThreadingWithLocation = 20; widthWithoutRankAndLocation = 20; widthWithoutThreading = 20; widthWithoutThreadingWithLocation = 20; }; 14 = { automaticInsertionOkay = 0; automaticInsertionWhileSearchingOkay = 0; columnIdentifier = 14; isVisible = 0; position = "-1"; positionWhileSearching = "-1"; widthWithLocation = 65; widthWithRank = 65; widthWithRankAndLocation = 65; widthWithThreading = 65; widthWithThreadingWithLocation = 65; widthWithoutRankAndLocation = 65; widthWithoutThreading = 65; widthWithoutThreadingWithLocation = 65; }; widthWithRankAndLocation = 75; widthWithThreading = 75; widthWithThreadingWithLocation = 75; widthWithoutRankAndLocation = 75; widthWithoutThreading = 264; widthWithoutThreadingWithLocation = 217; }; ... 9 = { automaticInsertionOkay = 0; automaticInsertionWhileSearchingOkay = 0; columnIdentifier = 9; isVisible = 0; position = "-1"; positionWhileSearching = "-1"; widthWithLocation = 20; widthWithRank = 20; widthWithRankAndLocation = 20; widthWithThreading = 20; widthWithThreadingWithLocation = 20; widthWithoutRankAndLocation = 20; widthWithoutThreading = 20; widthWithoutThreadingWithLocation = 20; }; }; normal = { 0 = { automaticInsertionOkay = 0; automaticInsertionWhileSearchingOkay = 0; columnIdentifier = 0; isVisible = 1; position = 1; positionWhileSearching = 1; widthWithLocation = 20; widthWithRank = 20; widthWithRankAndLocation = 20; widthWithThreading = 0; widthWithThreadingWithLocation = 0; widthWithoutRankAndLocation = 20; widthWithoutThreading = 20; widthWithoutThreadingWithLocation = 20; }; ... }; 9 = { automaticInsertionOkay = 0; automaticInsertionWhileSearchingOkay = 0; columnIdentifier = 9; isVisible = 0; position = "-1"; positionWhileSearching = "-1"; widthWithLocation = 20; widthWithRank = 20; widthWithRankAndLocation = 20; widthWithThreading = 20; widthWithThreadingWithLocation = 20; widthWithoutRankAndLocation = 20; widthWithoutThreading = 20; widthWithoutThreadingWithLocation = 20; }; }; outgoing = { 0 = { automaticInsertionOkay = 0; automaticInsertionWhileSearchingOkay = 0; columnIdentifier = 0; isVisible = 1; position = 1; positionWhileSearching = 1; widthWithLocation = 20; widthWithRank = 20; widthWithRankAndLocation = 20; widthWithThreading = 0; widthWithThreadingWithLocation = 0; widthWithoutRankAndLocation = 20; widthWithoutThreading = 20; widthWithoutThreadingWithLocation = 20; }; ... }; 9 = { automaticInsertionOkay = 0; automaticInsertionWhileSearchingOkay = 0; columnIdentifier = 9; isVisible = 0; position = "-1"; positionWhileSearching = "-1"; widthWithRank = 20; widthWithRankAndLocation = 20; widthWithThreading = 20; widthWithThreadingWithLocation = 20; widthWithLocation = 20; widthWithoutRankAndLocation = 20; widthWithoutThreading = 20; widthWithoutThreadingWithLocation = 20; }; }; }; ThreadingDefault = 0; TornOffToolbarIsHidden = 0; TrashViewerAttributes = { DisplayInThreadedMode = no; SearchSortDescending = YES; SearchSortOrder = rank; SortOrder = from; SortedDescending = NO; }; WebContinuousSpellCheckingEnabled = 1; WebKitShowsURLsInToolTips = 1; junkMailTrustHeaders = 1; }