Symptoms

Messages are not being sent/received and an error in OX log:

Jan 13, 2014 1:21:14 PM com.openexchange.log.internal.LoggerTask call
SEVERE: Logged at: com.openexchange.groupware.settings.impl.RdbSettingStorage.readSharedValue(RdbSettingStorage.java:398)
Problem while reading setting value.
com.openexchange.ajp13.remoteAddress=127.0.0.1
com.openexchange.ajp13.remotePort=59907
IMAP-1016 Category=5 Message=Connection was refused or timed out while attempting to connect to remote server <hostname> for user <mailname>. exceptionID=-48449585-19515
        at com.openexchange.groupware.settings.tree.modules.mail.folder.Sent$1.getValue(Sent.java:112)
        at com.openexchange.groupware.settings.impl.RdbSettingStorage.readSharedValue(RdbSettingStorage.java:393)
        at com.openexchange.groupware.settings.impl.RdbSettingStorage.readValues(RdbSettingStorage.java:337)
        at com.openexchange.groupware.settings.impl.RdbSettingStorage.readSubValues(RdbSettingStorage.java:413)
        at com.openexchange.groupware.settings.impl.RdbSettingStorage.readValues(RdbSettingStorage.java:333)
        at com.openexchange.groupware.settings.impl.RdbSettingStorage.readSubValues(RdbSettingStorage.java:413)
        at com.openexchange.groupware.settings.impl.RdbSettingStorage.readValues(RdbSettingStorage.java:333)
        at com.openexchange.groupware.settings.impl.RdbSettingStorage.readSubValues(RdbSettingStorage.java:413)
        at com.openexchange.groupware.settings.impl.RdbSettingStorage.readValues(RdbSettingStorage.java:333)
        at com.openexchange.ajax.Login.appendModules(Login.java:1226)
        at com.openexchange.ajax.Login.loginOperation(Login.java:1007)
        at com.openexchange.ajax.Login.doLogin(Login.java:968)
        at com.openexchange.ajax.Login$1.handleRequest(Login.java:188)
        at com.openexchange.ajax.Login.doJSONAuth(Login.java:742)
        at com.openexchange.ajax.Login.doGet(Login.java:729)
        at com.openexchange.ajax.Login.doPost(Login.java:867)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
        at com.openexchange.ajax.AJAXServlet.service(AJAXServlet.java:429)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:820)
        at com.openexchange.ajp13.coyote.AjpProcessor.process(AjpProcessor.java:845)
        at com.openexchange.ajp13.coyote.sockethandler.CoyoteTask.call(CoyoteTask.java:184)
        at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334)
        at java.util.concurrent.FutureTask.run(FutureTask.java:166)
        at com.openexchange.threadpool.internal.CustomThreadPoolExecutor$Worker.runTask(CustomThreadPoolExecutor.java:781)
        at com.openexchange.threadpool.internal.CustomThreadPoolExecutor$Worker.run(CustomThreadPoolExecutor.java:807)
        at java.lang.Thread.run(Thread.java:679)
Caused by: IMAP-1016 Category=5 Message=Connection was refused or timed out while attempting to connect to remote server <servername> for user <mailname>. exceptionID=-48449585-19514
        at com.openexchange.imap.IMAPException.create(IMAPException.java:977)
        at com.openexchange.imap.IMAPException.create(IMAPException.java:903)
        at com.openexchange.imap.IMAPAccess.checkTemporaryDown(IMAPAccess.java:1051)
        at com.openexchange.imap.IMAPAccess.connectInternal(IMAPAccess.java:777)
        at com.openexchange.mail.api.MailAccess.delegateConnectInternal(MailAccess.java:673)
        at com.openexchange.mail.api.MailAccess.connect0(MailAccess.java:631)
        at com.openexchange.mail.api.MailAccess.connect(MailAccess.java:554)
        at com.openexchange.mail.MailServletInterfaceImpl.initMailAccess(MailServletInterfaceImpl.java:1923)
        at com.openexchange.mail.MailServletInterfaceImpl.initConnection(MailServletInterfaceImpl.java:1900)
        at com.openexchange.mail.MailServletInterfaceImpl.getSentFolder(MailServletInterfaceImpl.java:1742)
        at com.openexchange.groupware.settings.tree.modules.mail.folder.Sent$1.getValue(Sent.java:106)
        ... 25 more

Cause

The connections are hitting limitation on qmail server. On qmail server in /var/log/maillog:

Jan 13 10:57:06 qmail-01 dovecot: imap-login: Maximum number of connections from user+IP exceeded (mail_max_userip_connections): user=<mailname>, method=PLAIN, rip=<IP>, lip=<IP>, TLS
Jan 13 10:57:43 qmail-01 dovecot: imap-login: Maximum number of connections from user+IP exceeded (mail_max_userip_connections): user=<mailname>, method=PLAIN, rip=<IP>, lip=<IP>, TLS
Jan 13 19:37:22 qmail-01 dovecot: imap-login: Maximum number of connections from user+IP exceeded (mail_max_userip_connections): user=<mailname>, method=PLAIN, rip=<IP>, lip=<IP>, TLS

Resolution

Consider increasing dovecot connection limits, by default it set to 10:

# grep mail_max_userip_connections /etc/dovecot.conf
  #mail_max_userip_connections = 10

Additional information

Please see the troubleshooting guide for Qmail at KB#121187

Internal content