IMAP capabilities

When you click on a domain at ?admin#/domains, you can disable capabilities on the IMAP tab. You can also do this at data/_data_/_default_/domains/*.json. This allows you to prevent errors in the IMAP server or improve speed.

By default a few capabilities are shown. If you want all capabilities that the server supports, you must hit the [Test] button WITH login credentials.

Below you will find info about each capability.

Used by SnappyMail

ACL / RIGHTS=

Allows a user to see which access permissions a certain folder/mailbox has. In the future this also allows the user to add/edit/delete the access for others.

APPENDLIMIT

This provides the ability to advertise a maximum upload size allowed by the IMAP server, so that we know the size limitation.

AUTH=*

Which type of login methods are allowed to use. Can be things like: LOGIN, PLAIN, SCRAM, etc.

BINARY

This lets the server perform content-type decoding prior to transmitting message data. When disabled, SnappyMail has to decode the data itself through PHP (in the future maybe through JavaScript). If the server fails in decoding, it is best to disable this capability.

CONDSTORE

This is a very important capability that allows for better cache handling by fetching the HIGHESTMODSEQ of the folder/mailbox. Also read QRESYNC

ENABLE

This enables features on the server. Currently 2 are used:

IMAP4rev1 to tell IMAP4rev2 server to use v1
UTF8=ACCEPT to tell the server we want to communicate in UTF-8 mode

LIST-EXTENDED

Allows to instantly fetch more folder/mailbox info with the LIST command. Like:

CHILDREN
SPECIAL-USE
SUBSCRIBED

Disabling this feature allows faster loading of the folders list. SnappyMail will then ask the status of each folder later in a queue.

LIST-STATUS

Allows to instantly fetch more folder/mailbox info with the LIST command. Like:

STATUS
MESSAGES
UNSEEN
UIDNEXT
UIDVALIDITY
HIGHESTMODSEQ (requires capability CONDSTORE or QRESYNC)
APPENDLIMIT
SIZE (requires capability STATUS=SIZE)
MAILBOXID (requires capability OBJECTID)

LITERAL+

METADATA

This is used to get more information about the folders. Like: comments, special-use and kolab folder type.

MOVE

NAMESPACE

OBJECTID

Is used to fetch the MAILBOXID of each folder/mailbox.

Cyrus mail server has a bug that crashes with this capability. In this case disable it.

PREVIEW

QRESYNC

When CONDSTORE is not available (disabled), this is used for better cache handling of the folder/mailbox.

SASL-IR

When enabled, this makes the login process faster.

SORT

SPECIAL-USE

Allows to know which folders/mailboxes are default for sent, archive, trash, etc.

STATUS=SIZE

Allows to show how much bytes the folders/mailboxes contains.

THREAD

Allows to show message threads

UIDPLUS

UNSELECT

WITHIN

Currently not used

CATENATE

CHILDREN

Returns the \haschildren or \hasnochildren flag on folders/mailboxes. This is handy to know if a certain folder/mailbox has children, but currently not used by because the complete mailbox hierarchy is loaded.

CONTEXT=SEARCH

ESEARCH

Used by \MailSo\ImapClient::MessageSimpleESearch() to fill the messages list

ESORT

Used by \MailSo\ImapClient::MessageSimpleESort() to fill the messages list

I18NLEVEL=1

ID

Used by \MailSo\ImapClient::ServerID()