Akonadiserver together with mysqld and kontact consumes one thread completely.

When I debug akonadi with akonadiconsole it spams stuff like this:

kontact-1644948879 (0xad8050) * 11 9 (NAME "Trash" MIMETYPE (message/rfc822 inode/directory) REMOTEID ".Trash" REMOTEREVISION "" RESOURCE "akonadi_imap_resource_0" VIRTUAL 0 CACHEPOLICY (INHERIT true INTERVAL 15 CACHETIMEOUT 60 SYNCONDEMAND true LOCALPARTS (ENVELOPE HEAD)) collectionquota "-1 -1" imapquota " " uidnext "1913" collectionflags "\\Answered \\Flagged \\Deleted \\Seen \\Draft $ATTACHMENT $REPLIED $FORWARDED $SENT $TODO $SIGNED \\*" uidvalidity "1331504821" ENTITYDISPLAY "(\"\" \"user-trash\" \"\" ())" timestamp "1373880624" SpecialCollectionAttribute "trash")
(and the like with all of my email folders)

I'm using an IMAP and a POP3 connection, whether or not indexing is enabled does not affect the issue. None of the programs report any error. I'm using Arch Linux, so mysql is actually mariadb. Maybe I should blame the db (or rather my configuration, which I didn't touch before). So I started the server explicitely (without success).

"systemctl status mysqls" reports

mysqld.service - MariaDB database server
Loaded: loaded (/usr/lib/systemd/system/mysqld.service; disabled)
Active: active (running) since Sa 2013-08-31 19:04:57 CEST; 1h 49min ago
Process: 2580 ExecStartPost=/usr/bin/mysqld-post (code=exited, status=0/SUCCESS)
Main PID: 2579 (mysqld)
CGroup: name=systemd:/system/mysqld.service
└─2579 /usr/bin/mysqld --pid-file=/run/mysqld/mysqld.pid

Aug 31 19:04:55 Samsung mysqld[2579]: 130831 19:04:55 InnoDB: Compressed tables use zlib 1.2.8
Aug 31 19:04:55 Samsung mysqld[2579]: 130831 19:04:55 InnoDB: Initializing buffer pool, size = 128.0M
Aug 31 19:04:55 Samsung mysqld[2579]: 130831 19:04:55 InnoDB: Completed initialization of buffer pool
Aug 31 19:04:55 Samsung mysqld[2579]: 130831 19:04:55 InnoDB: highest supported file format is Barracuda.
Aug 31 19:04:55 Samsung mysqld[2579]: 130831 19:04:55 InnoDB: Waiting for the background threads to start
Aug 31 19:04:56 Samsung mysqld[2579]: 130831 19:04:56 Percona XtraDB (http://www.percona.com) 5.5.32-MariaDB-30.2 started; log sequence number 1597945
Aug 31 19:04:56 Samsung mysqld[2579]: 130831 19:04:56 [Note] Event Scheduler: Loaded 0 events
Aug 31 19:04:56 Samsung mysqld[2579]: 130831 19:04:56 [Note] /usr/bin/mysqld: ready for connections.
Aug 31 19:04:56 Samsung mysqld[2579]: Version: '5.5.32-MariaDB-log' socket: '/run/mysqld/mysqld.sock' port: 0 Source distribution
Aug 31 19:04:57 Samsung systemd[1]: Started MariaDB database server.

What can I do to solve the problem?

Are you using a system-wide MySQL instance for Akonadi?

I'm not aware to use sql anywhere else. Akonadi setting is 'use local sql server'.

Ok, then don't be fooled by what systemctl says (which is the system-wide instance, and not your local one). Are your accounts big? If not I would suggest to create a fresh user account and see whether the issue persists there (local vs global configuration issue).

What exactly do you have in mind with 'recreate the account'? Removing user account or mail accounts and/or all stuff from .local/... folders?

Edit: Akonadi is still checking mail folders after I removed both mail accounts (pop3 and imap) as well as the local folder (which was recreated immediately).

No, create a new user account (login), log in there, start KMail and check with one of the accounts (you'll have to recreate it). if it works, it's a local configuration issue; if it doesn't (same problem as your "regular" user account) the issue lies elsewhere.

Well, the test account works flawless (good idea!). And after relogin my normal, previously cleaned account was okay too. Since the issue concerns my mobile device, I can easily delete and recreate the mail accounts. Finally, I was able to fix my problem but I'm afraid that's not a real solution.