{"id":3826,"date":"2013-03-25T12:46:13","date_gmt":"2013-03-25T10:46:13","guid":{"rendered":"http:\/\/www.limilabs.com\/blog\/?p=3826"},"modified":"2015-07-30T16:12:53","modified_gmt":"2015-07-30T14:12:53","slug":"gmail-special-use-capability-is-broken","status":"publish","type":"post","link":"https:\/\/www.limilabs.com\/blog\/gmail-special-use-capability-is-broken","title":{"rendered":"Gmail’s SPECIAL-USE capability is broken"},"content":{"rendered":"

Recently it came to my attention that Gmail’s XLIST command is deprecated<\/a>.<\/p>\n

XLIST is a custom Gmail command<\/a> that retrieves information about the folder purpose, without the need of knowing the folders name. It works by returning additional flags, such as \\Spam, for folders of a known purpose (e.g. “[Gmail]\/Spam”)<\/p>\n

More standardized feature, deigned for the same purpose, is SPECIAL-USE extension.<\/p>\n

Both XLIST and SPECIAL-USE<\/a> are supported by Mail.dll. You can use CommonFolders<\/em> class to get folder by its function.<\/p>\n

On this site Gmail claims that:<\/p>\n

Gmail supports <\/strong>the IMAP LIST Extension for Special-Use Mailboxes [RFC 6154]<\/a>, which provides new attributes for special folders.<\/p><\/blockquote>\n

And in the next paragraph: <\/p>\n

The Gmail-specific XLIST command is deprecated <\/strong>in favor of the IMAP Special-Use List Standard [RFC 6154]<\/a>. <\/p><\/blockquote>\n

The problem is that their Special-Use support is seriously broken.<\/p>\n

Broken CAPABILITY response<\/h2>\n

RFC 6154 clearly states:<\/p>\n

Supporting implementations MUST <\/strong>include the “SPECIAL-USE” capability string in response to an IMAP CAPABILITY command.<\/p><\/blockquote>\n

Here’s the Gmail’s response to CAPABILITY command:<\/p>\n

Initial:<\/p>\n

\r\nS: * OK Gimap ready for requests from 89.67.10.122 z2if15323304eeo.17\r\nC: f3a21e43c6c648e8 CAPABILITY\r\nS: * CAPABILITY IMAP4rev1 UNSELECT IDLE NAMESPACE QUOTA ID XLIST CHILDREN X-GM-EXT-1 XYZZY SASL-IR AUTH=XOAUTH AUTH=XOAUTH2\r\n<\/pre>\n
After logging in:<\/p>\n
\r\n C: 77776ad235694614 CAPABILITY\r\n S: * CAPABILITY IMAP4rev1 UNSELECT IDLE NAMESPACE QUOTA ID XLIST CHILDREN X-GM-EXT-1 UIDPLUS COMPRESS=DEFLATE ENABLE MOVE\r\n S: 77776ad235694614 OK Success\r\n<\/pre>\n
There is no “SPECIAL-USE” capability returned. What is funny deprecated XLIST is still there.<\/p>\n
Broken LIST response<\/h2>\n
RFC 6154 clearly states:<\/p>\n
If the client specifies the “SPECIAL-USE” return option, the LIST command MUST <\/strong>return the new special-use attributes on those mailboxes that have them set.\n<\/p><\/blockquote>\n
Gmail server fails to parse such command:<\/p>\n
\r\nC: 7ab9a06868fa4717 LIST "" * RETURN (SPECIAL-USE)\r\nS: 7ab9a06868fa4717 BAD Could not parse command\r\n<\/pre>\n
Correct LIST response?<\/h2>\n
It seems however that regular LIST response contains flags defined in RFC 6154<\/a> (\\All, \\Flagged, \\Junk and so on):<\/p>\n
\r\n* LIST (\\HasNoChildren) "\/" "INBOX"\r\nS: * LIST (\\Noselect \\HasChildren) "\/" "[Gmail]"\r\nS: * LIST (\\HasChildren \\HasNoChildren \\All) "\/" "[Gmail]\/All Mail"\r\nS: * LIST (\\HasNoChildren \\Drafts) "\/" "[Gmail]\/Drafts"\r\nS: * LIST (\\HasChildren \\HasNoChildren \\Important) "\/" "[Gmail]\/Important"\r\nS: * LIST (\\HasChildren \\HasNoChildren \\Sent) "\/" "[Gmail]\/Sent Mail"\r\nS: * LIST (\\HasChildren \\HasNoChildren \\Junk) "\/" "[Gmail]\/Spam"\r\nS: * LIST (\\HasChildren \\HasNoChildren \\Flagged) "\/" "[Gmail]\/Starred"\r\nS: * LIST (\\HasChildren \\HasNoChildren \\Trash) "\/" "[Gmail]\/Trash"\r\n<\/pre>\n
The response follows the Special-Use standard with an additional \\Important attribute added for Gmail’s Priority Inbox<\/p><\/blockquote>\n
Why not X-Important?<\/p>\n","protected":false},"excerpt":{"rendered":"
Recently it came to my attention that Gmail’s XLIST command is deprecated. XLIST is a custom Gmail command that retrieves information about the folder purpose, without the need of knowing the folders name. It works by returning additional flags, such as \\Spam, for folders of a known purpose (e.g. “[Gmail]\/Spam”) More standardized feature, deigned for […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4],"tags":[98,25,28],"class_list":["post-3826","post","type-post","status-publish","format-standard","hentry","category-mail-dll","tag-bug","tag-gmail","tag-imap"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/www.limilabs.com\/blog\/wp-json\/wp\/v2\/posts\/3826"}],"collection":[{"href":"https:\/\/www.limilabs.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.limilabs.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.limilabs.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.limilabs.com\/blog\/wp-json\/wp\/v2\/comments?post=3826"}],"version-history":[{"count":22,"href":"https:\/\/www.limilabs.com\/blog\/wp-json\/wp\/v2\/posts\/3826\/revisions"}],"predecessor-version":[{"id":4956,"href":"https:\/\/www.limilabs.com\/blog\/wp-json\/wp\/v2\/posts\/3826\/revisions\/4956"}],"wp:attachment":[{"href":"https:\/\/www.limilabs.com\/blog\/wp-json\/wp\/v2\/media?parent=3826"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.limilabs.com\/blog\/wp-json\/wp\/v2\/categories?post=3826"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.limilabs.com\/blog\/wp-json\/wp\/v2\/tags?post=3826"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}