We are using the latest SmarterMail v15 and have ~5000 users doing 50K incoming and 50K outgoing emails daily.
Every day during peak hours we are seeing 1000-6000 emails stuck in queue. Even status Delivered are stuck in queue with a next attempt listed. There are hundreds of emails in Delivery Delay and Local Delivery status.
We have 2x256GB SSD RAID1 for the spool and 10x4TB SATA enterprise 6gbps in RAID10 for the mailbox storage.
We are seeing Read queue averaging 0.5 and write queue averaging 0.8 during peak hours.
We have tried reducing indexing to 1 thread as well as completely disabling it during peak hours.
We have a E5-2620 6 core / 12 thread CPU which seems to be hitting 100% at times. RAM usage is normal < 10%
What could be the reason for the spool getting stuck ? We have disabled antivirus completely and reduced antispam rules to the bare minimum. We also tried adding another physical server as an outgoing gateway for some of the heavy users, it did not help.
At times, we are seeing 0 emails sent in last 5 minutes. Also , the count in Spool Dashboard is different from the one in All messages. We have to restart SmarterMail service multiple times a day to allow mails to start getting sent.