This document describes how the SquirrelMail address book works. It is
primarily intended for developers.
1. The Basics
The address book is written using PHP classes, with one class,
AddressBook, that use one or more "backend" classes to access
different address books.
All operations, such as search, lookup, add etc., are performed by
calling the appropriate methods from the AddressBook object. The
operation will then be distributed by calling the correct method in
the appropriate backend(s).
To initialize the address book, the function addressbook_init() from
functions/addressbook.php is called. This function will create an
AddressBook object, add one backend for a personal address book (file
based storage), and add the LDAP backends defined in the $ldap_server
configuration directive (if any).
An addressbook can also be initialized like this if you want to:
$abook = new AddressBook;
// Add one file based backend (personal address book)
$abook->add_backend("local_file", Array("filename" => $filename,
"create" => true));
$abook->add_backend("ldap_server", <array with parameters>);
$res = $abook->search("John Doe");
echo $res["name"] . " " . $res["email"];
2. The AddressBook class
This class acts as the glue for the address book. The following public
methods are provided:
NAME - The name of the backend to add. A file with a
class abook_NAME must be included before this can
PARAMETERS - A mixed variable that is passed on to
the backend class constructor. See each backend
This method will return a backend ID number (not usable at the
moment), or false if it failed.
QUERY - Something to search for. At the moment, only
a string is allowed here, but advanced expressions
will be supported through an array of parameters.
BNUM - Optional backend number to search.
This method will return an array of result arrays (see below), an
empty array if nothing was found, or false if the search failed.
The same as search(), but the result array is sorted by backend and
fullname before it is returned.
NICKNAME - Return the user identified by NICKNAME in
BNUM - ID of the backend to look in (optional).
This method will return one result array (see below), an empty
array if nothing was found, or false if the search failed. The
lookup is only performed in "local" type backends.
This method will return an array of result arrays (see below) for
all addresses in the addressbook, or false if it failed. Only
addresses in "local" type backends are returned.
USERDATA - An array with user data. Must contain the following
keys: nickname, firstname, lastname, email, label
See below for information about the keys.
BNUM - ID of the backend, as returned by add_backend, to add this
This method will return the backend ID of the backend where data
was added, or false if it failed.
NICKNAME - Delete the user identified by NICKNAME in the
addressbook or, if NICKNAME is an array, all users indentified by
nthe nicknames in the array.
BNUM - ID of the backend, as returned by add_backend, to remove
the user(s) from.
This method will retrun true if the user(s) was removed, or false
if removal failed.
modify(NICKNAME, USERDATA, BNUM)
NICKNAME - Update the user identified by NICKNAME in the
USERDATA - Array with user data. The exisiting data for the user
will be replaced with this.
BNUM - ID of the backend, as returned by add_backend, to update
the user in.
This method will retrun true if the user was modified, or false if
If one of the above methods fail, an error message is available in the
AddressBook->error variable. Feel free to ignore it.
For the result of a search, lookup or list_addr, one or more result
arrays are used. These arrays contain the following keys:
nickname: Unique identifier for this name in this backend. Only
usable for the local_file backend, and possibly LDAP.
name: Person's full name.
email: Person's e-mail address.
backend: Backend ID where this was found
source: Name of the backend where this was found
In addition, the following keys may exist for some backends:
label: Additional information about the person
firstname: Person's first name
lastname: Person's last name
3. The backend classes
... more later ...
Ask firstname.lastname@example.org if you have any questions on how to build
new address book backends.
makeComposeLink() PHP function helps to create links to the compose page
easily, taking into account the user's settings, "Compose in new window" and
1) Build the last part of the URL as follows:
$comp_uri = 'src/compose.php?mailbox='.$mailboxbox.'&send_to='.urlencode($usermail);
2) The display part of the link can be anything you like (such the name of the user):
$disp = 'The user's name';
3) Print it:
echo makeComposeLink($comp_uri, $disp);
makeComposeLink() has been available since SquirrelMail 1.4.2.
the function needs one argument:
1) url with arguments to the compose window.
An IMAP server developed at Carnegie Mellon University
Tested Cyrus IMAP4 v2.2.12-Invoca-RPM-2.2.12-6.fc4
CAPABILITY IMAP4 IMAP4rev1 ACL QUOTA LITERAL+ MAILBOX-REFERRALS NAMESPACE
UIDPLUS ID NO_ATOMIC_RENAME UNSELECT CHILDREN MULTIAPPEND BINARY SORT
THREAD=ORDEREDSUBJECT THREAD=REFERENCES ANNOTATEMORE IDLE LISTEXT
PERMANENTFLAGS (\Answered \Flagged \Draft \Deleted \Seen $MDNSent \*)
NAMESPACE (("INBOX." ".")) (("user." ".")) (("shared." "."))
Server supports server side sorting since 2.0.4 version. euc-jp, euc-kr,
tis-620, cp1251, cp1255 character sets are not supported by sorting functions
Site URL: http://asg.web.cmu.edu/cyrus/
Part of University of Washington IMAP toolkit.
Tested 2002e (2003.339)
CAPABILITY IMAP4REV1 IDLE NAMESPACE MAILBOX-REFERRALS BINARY UNSELECT SCAN SORT
THREAD=REFERENCES THREAD=ORDEREDSUBJECT MULTIAPPEND LOGIN-REFERRALS STARTTLS
PERMANENTFLAGS (Seen \* \Answered \Flagged \Deleted \Draft \Seen)
NAMESPACE (("" "/")("#mhinbox" NIL)("#mh/" "/")) (("~" "/")) (("#shared/" "/")("#ftp/" "/")("#news." ".")("#public/" "/"))
Server supports server side sorting. Plain text logins are disabled by default.
Version visible in IMAP greeting can be used by more than one packaged version.
Site URL: http://www.washington.edu/imap/
Fast, scalable, enterprise IMAP server that uses Maildirs
CAPABILITY IMAP4rev1 UIDPLUS CHILDREN NAMESPACE THREAD=ORDEREDSUBJECT
THREAD=REFERENCES SORT QUOTA IDLE ACL ACL2=UNION
PERMANENTFLAGS (\* \Draft \Answered \Flagged \Deleted \Seen)
NAMESPACE (("INBOX." ".")) NIL (("#shared." ".")("shared." "."))
Recent (3.0.0+) versions support most of character sets used by SquirrelMail,
if courier-imap is compiled with --enable-unicode option. Only koi8-u
is not supported. Server can be compiled with custom number of supported
character sets. Sorting can be disabled in imapd configuration. Capability
string can be set in configuration. Supports CRAM-MD5, CRAM-SHA1 and
CRAM-SHA256, if userdb or other backend stores passwords in plain text. Does
not handle traditional mailbox files.
Site URL: http://www.courier-mta.org/
Open source email server for WinNT and later.
Tested 4.1.1 (Build 140).
CAPABILITY IMAP4 IMAP4rev1 QUOTA
PERMANENTFLAGS (\Deleted \Seen \Draft \Answered \Flagged)
Site URL: http://hmailserver.com/
Mercury Mail Transport System. Free email server for Win32 and Netware.
Tested Win32 v.4.01b
CAPABILITY IMAP4rev1 X-MERCURY
PERMANENTFLAGS (\Deleted \Draft \Seen \Answered)
* Server side sorting and threading are not supported.
* Message flags are not supported.
* IMAP folders can store messages _or_ other folders.
* Supports STARTTLS, if configured.
* May have issues with 8bit IMAP folder names.
Site URL: http://pmail.com/
Dovecot Secure IMAP server.
CAPABILITY IMAP4rev1 SORT THREAD=REFERENCES MULTIAPPEND UNSELECT LITERAL+ IDLE
CHILDREN LISTEXT LIST-SUBSCRIBED NAMESPACE
PERMANENTFLAGS (\Answered \Flagged \Deleted \Seen \Draft \*)
IMAP server supports server side sorting and threading. 1.0alpha1-5 versions
violate syntax of responses to UID commands. NAMESPACE is supported in 1.0alpha.
Remote plain text logins are disabled by default.
Site URL: http://dovecot.org/
Simple, lightweight IMAP server.
Tested v.1.2.13 and 1.3.4
CAPABILITY IMAP4rev1 STARTTLS AUTH=LOGIN AUTH=PLAIN (1.2.13)
CAPABILITY IMAP4rev1 STARTTLS AUTH=LOGIN AUTH=PLAIN IDLE LITERAL+ NAMESPACE
PERMANENTFLAGS (\Answered \Flagged \Deleted \Seen \Draft) - 1.2.13
PERMANENTFLAGS (\Answered \Flagged \Deleted \Seen \Draft \*) - 1.3.4
IMAP server does not support server side sorting and threading. Plain text
logins are disabled by default. Due to available storage backend configuration
options it is impossible to create single preset, which covers all setups.
Site URL: http://bincimap.org/
GNU Mailutils IMAPD
Part of GNU mail utility collection
Tested v.0.6.1 (Debian Sarge) and v.0.6.90
CAPABILITY IMAP4rev1 NAMESPACE IDLE X-VERSION AUTH=GSSAPI AUTH=ANONYMOUS
AUTH=EXTERNAL AUTH=PLAIN AUTH=LOGIN AUTH=SECURID AUTH=DIGEST-MD5 AUTH=CRAM-MD5
PERMANENTFLAGS (\Answered \Deleted \Seen)
NAMESPACE (("" "/")) NIL NIL
Can use UW preset. Server side sorting is not supported. IMAP folders can
store messages or subfolders. Can't create second level (mail/Folder/Subfolder/)
subfolders. Invalid unseen message count, when \Seen flag is toggled manually.
Folder listing with non-default sort order issues are fixed in cvs version.
Use of server with SquirrelMail is not recommended and not supported.
Site URL: http://savannah.gnu.org/projects/mailutils
IMAP server that is part of DBMail email suite. DBMail provides local delivery
agent, pop3 and imap servers. User information and emails are stored in
Information provided by Muhd Zamri
CAPABILITY IMAP4 IMAP4rev1 AUTH=LOGIN ACL NAMESPACE SORT
PERMANENTFLAGS (\Seen \Answered \Deleted \Flagged \Draft \Recent)
NAMESPACE (("" "/")) (("#Users" "/")) (("#Public" "/"))
IMAP server provides partial support of IMAP QUOTA extension. setquota command
is not supported and QUOTA extension is not advertised in CAPABILITY. SORT
extension is broken in tested version.
> A05 UID SORT (FROM) US-ASCII ALL
A05 BAD syntax error in sort keys
> A06 UID SORT (FROM) ISO-8859-1 ALL
A06 BAD UID command received in invalid state
Site URL: http://dbmail.org/
HTTP and email server written in Java. User information is stored in database.
SELECT response is in RFC 2060 format.
PERMANENTFLAGS - missing
FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
Site URL: http://www.bejy.net
Mac OS X
No clear information about used software. Some OS X versions might use Eudora
Internet Messaging Suite (EIMS, http://eudora.com/eims/), some - Apple IMAP
server, some - Cyrus.
Exchange IMAP service
IMAP server included in proprietary Exchange Server, Microsoft messaging and
Server does not support server side sorting.
PMDF is a proprietary, high performance, standards-based Internet messaging
product suite for Windows, OpenVMS, Tru64 UNIX, and Solaris.
Tested IMAP4rev1 Server PMDF V6.2-X29.1
CAPABILITY IMAP4 IMAP4REV1 NAMESPACE X-NON-HIERARCHICAL-RENAME AUTH=LOGIN
PERMANENTFLAGS (\Answered \Flagged \Deleted \Seen)
NAMESPACE (("" "/")) NIL NIL
Supports TLS and SSL encryption, SASL CRAM-MD5 and DIGEST-MD5 authentication.
Includes SIEVE (RFC 3028) support.
Site URL: http://process.com/tcpip/pmdf.html
Merak IMAP server
Proprietary IMAP server included in Merak Email Server Suite.
Tested 8.3.0.r and 8.3.1 beta.
CAPABILITY IMAP4rev1 AUTH=CRAM-MD5 AUTH=DIGEST-MD5 AUTH=LOGIN AUTH=PLAIN SORT
THREAD-ORDEREDSUBJECT UIDPLUS QUOTA ACL NAMESPACE STARTTLS
PERMANENTFLAGS (\Seen \Answered \Flagged \Draft \Deleted)
NAMESPACE (("" "/")) NIL NIL
INBOX folder is lowercased. IMAP folder names are case insensitive. Possible
issue with IMAP SORT extension.
A005 UID SORT (DATE) ISO-8859-1 ALL
* UID SORT 1 2
UID SORT Completed
SquirrelMail expects '* SORT 1 2'
Site URL: http://www.icewarp.com
MailSite IMAP server
Commercial email server for Windows.
Tested 18.104.22.168 version.
CAPABILITY IMAP4rev1 ACL NAMESPACE UIDPLUS AUTH=NTLM AUTH=SCRAM-MD5
PERMANENTFLAGS (\Answered \Flagged \Deleted \Seen \Draft \*)
NAMESPACE (("" "/")) (("#shared/" "/")) NIL
FETCH response to UID STORE command violates RFC 3501.
Site URL: http://rockliffe.com/
IMAP server ready H mproxyus4
Unidentified IMAP server or IMAP proxy used by 1&1 Internet Inc.
(http://1and1.com/ and http://1und1.de/)
CAPABILITY CHILDREN ID IDLE IMAP4 IMAP4rev1 LITERAL+ LOGIN-REFERRALS
MAILBOX-REFERRALS NAMESPACE UIDPLUS QUOTA STARTTLS AUTH=PLAIN AUTH=LOGIN
The intended audience for this document are people who want to understand how
the MIME code works. This is a technical documentation of how mime.php
works and how it parses a MIME encoded message.
There are two objects that are used: "message" and "msg_header". Here is a
brief overview of what each object contains.
Contains variables for all the necessary parts of the header of a
message. This includes (but is not limited to) the following: to, from,
subject, type (type0), subtype (type1), filename ...
This contains the structure for the message. It contains two parts:
$header and $entities. $header is of type msg_header, and $entities
is an array of type $message. The $entities array is optional. If
it does not exist, then we are at a leaf node, and have an actual
attachment (entity) that can be displayed. Here is a tree view of how
this object functions.
| +--- header
| +--- header
Getting the Structure
Previously (version 0.4 and below), SquirrelMail handled all the parsing of
the email message. It would read the entire message in, search for
boundaries, and create an array similar to the $message object described
above. This was very inefficient.
Currently, all the parsing of the body of the message takes place on the
IMAP server itself. According to RFC 2060 section 7.4.2, we can use the
BODYSTRUCTURE function which will return the structure of the body (imagine
that). It goes into detail of how the bodystructure should be formatted,
and we have based our new MIME support on this specification.
A simple text/plain message would have a BODYSTRUCTURE similar to the
("TEXT" "PLAIN" ("CHARSET" "US-ASCII") NIL NIL "7BIT" 1152 23)
A more complicated multipart message with an attachment would look like:
(("TEXT" "PLAIN" ("CHARSET" "US-ASCII") NIL NIL "7BIT" 1152 23)("TEXT"
"PLAIN" ("CHARSET" "US-ASCII" "NAME" "cc.diff")
"<email@example.com>" "Compiler diff" "BASE64"
4554 73) "MIXED"))
Our MIME functionality implements different functions that recursively
run through this text and parses out the structure of the message. If you
want to learn more about how the structure of a message is returned with
the BODYSTRUCTURE function, please see RFC 2060 section 7.4.2.
NOTE: SquirrelMail passes the MIME Torture Test written by Mark
Crispin (author of the IMAP protocol). This message is crazy! It
has about 30 parts nested inside each other. A very good test,
and SquirrelMail passed it. It can be found here:
Getting the Body
Once all the structure of the message has been read into the $message
object, we then need to display the body of one entity. There are a number
of ways we decide which entity to display at a certain time, and I won't go
into that here.
Each entity has its own ID. Entity IDs look something like "1.2.1", or
"4.1", or just "2". You can find a detailed description of how entities
should be identified by reading RFC 2060 section 6.4.5. To fetch the body
of a particular entity, we use the function "BODY[<section>]". For
instance, if we were wanting to return entity 1.2.1, we would send the
IMAP server the command: "a001 FETCH <msg_id> BODY[1.2.1]".
This returns a string of the entire body. Based upon what is in the header,
we may need to decode it or do other things to it.
That is basically how it works. There is a variable in mime.php called
$debug_mime that is defined at the top of that file. If you set it to true,
it will output all kinds of valuable information while it tries to decode
the MIME message.
The code in mime.php is pretty well documented, so you might want to poke
around there as well to find out more details of how this works.
If you have questions about this, please direct them to our mailing list:
In order to get correct folder deletion across the board for all
different RFC 2060 compliant IMAP servers, deleting of folders
needed to work by deleting subfolders (inferiors) first, working
up to the top folder that is desired to be deleted.
The best way to do this was to use a tree, and walk the thing in
preorder to get subfolders first (leaves), working our way up the
tree. I chose to use an array for the tree structure.
The array has the following elements:
$tree["value"] = <full folder name>
$tree["doIHaveChildren"] = boolean
$tree["subNodes"] = indexes of the array that are
child nodes of this node
The trickiest part was finding the correct parent node when creating
a new node in the tree. Check the documentation in the code for
more info on this.
Basically all we had to do was loop through each of the items that
need to be in the tree (folders, subfolders), find their parent,
let their parent know it has a new child, and insert the values
into the child.
Once the tree is generated, a simple preorder or postorder walk
of the tree can be done doing whatever function you desire (delete,
Preorder walking gives you the tree from the leaves up. Postorder
walks the tree from the root node down to the leaves.