Question Failed emails gets re-added to the queue, resulting in a huge queue


I'm not sure where the problem lies at the moment, this may be a Xenforo issue, but thought I'd run it passed this forum first.

I moved the website to a new server, little configuration was required as both server are similar. the forum was running fine, but later found out the connection to the mail server wasn't there, this was a server config. So nothing to do with the forum.
In the Xenforo server error log, there were many failed attempts to send an email. Its a small forum, only a few people have asked for an email reply when a thread was replied to. So there was about 10 email due to go out. As these emails couldn't go out, for some reason they got re-added to be sent again. so some members got the same email over 100 times, and it was still resending over and over. To stop this happening again I have edited setting on the server to only allow 250 emails per hour, this is plenty for regular use and even covers the newsletter that gets sent out.

So thinking that I have sorted users getting multiple emails. A few weeks of no issues. Until this morning, sent a newsletter using DragonByte Mail yesterday. A users email address had changed so couldn't be delivered,
Checking the Xenforo server log
  • Swift_TransportException: Email to failed: Expected response code 250 but got code "554", with message "554 5.7.0 Your message could not be sent. The limit on the number of allowed outgoing messages was exceeded. Try again later. "
  • src/vendor/swiftmailer/swiftmailer/lib/classes/Swift/Transport/AbstractSmtpTransport.php:383
  • Generated by: Unknown account
  • 1 Aug 2020 at 9:09 AM
Checking the server data base there are 200,000 emails in there. Luckily i have this server restriction in place. The queue is getting larger and larger by the hour and if i didn't service this then I'd have issues of the server falling over. Also the email address isn't valid anymore, however if this email address did become live again then this entire queue would be sent out to them, probably go on for infinity as emails are being repeatedly added to the queue faster than they can go out.

So what solution am i looking for? well this may not be a DragonByte mail issue, and more of a queuing issue from Xenforo. If an email fails, then pop it in the log and don't re-add it to the queue, the queue shouldn't grow exponentially like that, and I don't know the cause of it. Maybe there is a setting issue else I'm sure someone would have pointed this out before if its a true bug.

Fillip H.

Staff member
This is definitely not a DB Mail issue. XenForo will queue mail for retry up to 3 times, after which is it permanently dropped.

You should move to a better host that does not have outgoing mail restrictions.


Thanks Fillip.
I can control the outgoing mail restrictions, it was unrestricted but due to the mail queue squirting out thousands of repeated emails over night to the same people i didn't trust the mail queue not to do it again so implemented a mail restriction that texts me when the limit is exceeded.
I don't think its a DB Mail issue and more of a Xenforo mail queue. So i will investigate that route now. Many thanks for your reply. Its given me direction to go next.

DragonByte Mail

XenForo 1.5.3+ XenForo 2.0.x XenForo 2.1.x XenForo 2.2.x
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