After upgrade of Gentoo package kdepim-runtime to 4.12.97 (akonadi-server version is 1.11.90) it became impossible to view message from IMAP mailboxes. Local folders work fine. Here is the log for localhost IMAP server when I tried to read a message from Akonadi Console.

akonadiconsole-636708761 (0x11aea90) 31 UID FETCH 30542 FULLPAYLOAD ALLATTR EXTERNALPAYLOAD (UID COLLECTIONID FLAGS SIZE REMOTEID REMOTEREVISION TAGS DATETIME) 
akonadi_imap_resource_0 (0x1121510) 267 UID FETCH 30542 CACHEONLY ANCESTORS INF EXTERNALPAYLOAD (UID COLLECTIONID FLAGS SIZE REMOTEID REMOTEREVISION DATETIME) 
akonadi_imap_resource_0 (0x1121510) * 30542 FETCH (UID 30542 REV 2 REMOTEID "3918" MIMETYPE "message/rfc822" COLLECTIONID 40 SIZE 4293 DATETIME "01-Mar-2014 21:26:18 +0000" FLAGS (\SEEN) ANCESTORS ((40 ".Gentoo") (26 ".bugzilla") (18 "imap://eugene@localhost/") (0 ""))) 
akonadi_imap_resource_0 (0x1121510) 267 OK UID FETCH completed 
akonadi_imap_resource_0 (0x1121510) 268 UID STORE 30542 NOREV (REMOTEID "3918" SILENT PLD:HEAD[1] {3702} 
akonadi_imap_resource_0 (0x1121510) 268 NO PartTypeException: Invalid part type name. 
akonadiconsole-636708761 (0x11aea90) 31 NO Unable to fetch item from backend (collection 0) : Unable to retrieve item from resource: NO PartTypeException: Invalid part type name. 
akonadiconsole-636708761 (0x11aea90) 32 UID FETCH 30542 FULLPAYLOAD ALLATTR EXTERNALPAYLOAD (UID COLLECTIONID FLAGS SIZE REMOTEID REMOTEREVISION TAGS DATETIME) 
akonadi_imap_resource_0 (0x1121510) 270 UID FETCH 30542 CACHEONLY ANCESTORS INF EXTERNALPAYLOAD (UID COLLECTIONID FLAGS SIZE REMOTEID REMOTEREVISION DATETIME) 
akonadi_imap_resource_0 (0x1121510) * 30542 FETCH (UID 30542 REV 2 REMOTEID "3918" MIMETYPE "message/rfc822" COLLECTIONID 40 SIZE 4293 DATETIME "01-Mar-2014 21:26:18 +0000" FLAGS (\SEEN) ANCESTORS ((40 ".Gentoo") (26 ".bugzilla") (18 "imap://eugene@localhost/") (0 ""))) 
akonadi_imap_resource_0 (0x1121510) 270 OK UID FETCH completed 
akonadi_imap_resource_0 (0x1121510) 271 UID STORE 30542 NOREV (REMOTEID "3918" SILENT PLD:HEAD[1] {3702} 
akonadi_imap_resource_0 (0x1121510) 271 NO PartTypeException: Invalid part type name. 
akonadiconsole-636708761 (0x11aea90) 32 NO Unable to fetch item from backend (collection 0) : Unable to retrieve item from resource: NO PartTypeException: Invalid part type name.