Emails got stuck in spool
Question asked by Michael Andrews - 6/16/2020 at 2:39 PM
I'm trying to track down why all of a sudden emails stopped sending out yesterday for us. I've looked through all the logs and everything looks like it delivered just fine. However, no emails were going out, we verified this with all of our emails. As soon as I reset the service, things started sending again. I'm just trying to track down why this happened and how I can be sure to put checks in, to make sure it doesn't happen again.

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Kyle Kerst Replied
Employee Post
Hello Michael, I'm sorry to hear you're having spooling issues. Your best bet is to submit a ticket on this so we can review your logs in more detail I think. In the meantime, the majority of spool backups are typically caused by DNS lookup failures or temporary issues preventing SMTP from completing successfully. To this end I usually recommend doing two things to resolve these issues long term. First, head over to Settings>General and confirm you have at least one public DNS server (or DNS server outside of your network) set up here to ensure you have a fallback DNS server to use in the event your internal one goes down. I use these: (Cloudflare DNS) (Google DNS)

Next, delayed spam checks can cause these types of issues as well, and I recommend we look for any slow responding spam checks. Head over to Settings>Antispam and look for any entries under RBLs/URIBLs showing high response times and disable them to see if this resolves your spooling issues. Let me know how it goes as you find out more on this. Have a good one!
Kyle Kerst
Technical Support Specialist
SmarterTools Inc.
(877) 357-6278
Try to disable TLS on SMTP Out:

echoDreamz Replied
Note that using public dns servers will most likely break RBL lookups. So be careful with that. 

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