I started a mailing yesterday using Administer->System Settings->Scheduled Jobs->Send Scheduled Mailings->More->Execute Now. The job started and sent about 5000 of 7000 emails but then seemed to hang. Over 2000 remain unsent, and the job log shows "Started..." but not "Finished...", and the status of the job is "Running." It's been more than a day since I started the job. Any idea what's going on?
Do you have a cron job configured for CiviCRM that runs periodically?
Can you check CiviCRM and/or Apache Error log for any errors?
Scheduled Mailing jobs are executed in batches of 1000 or the batch limit specified under Administer >> CiviMail >> Mailer Settings.
If the recent Schedule job log says 'Started' then the last job was terminated because of error. This might be for several reasons like php time out, memory allocation, mysql connection time out, DB errors etc. To trace the problem you will need to check CiviCRM and Apache logs to see if any errors were recorded.
To complete the job you can re run the Send Scheduled Mailings manually if your system is not configured to do it automatically.
Have you tried manually running the job again? It's likely that you hit the maximum time for the process on your server and that is why it's hanging. I seem to remember having to do that when we did a large mailing before we got the ability to increase all of our PHP settings.