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Queues

Most messages are delivered within seconds. When the recipient's mail server can't take a message straight away, for example because it limits how fast it accepts mail or is temporarily unavailable, Mumara ONE keeps the message in a delivery queue and retries it automatically.

A queue holds the waiting messages for one recipient domain (such as a mailbox provider) sent through one of your pools. Analytics → Queues shows the queues that have mail in them right now. The page is titled Queues Summary.

Queues are live, not historical

This page doesn't have a period list: it shows the state of your queues at the moment you open it. Reload the page to see the latest figures. A message leaves its queue as soon as it's delivered or bounces.

Queue Total​

The top card shows Queue Total, the number of queues that have mail waiting, and a line such as "1,240 emails are in the 6 queues and scheduled for the delivery".

Top 10 Queues​

The Top 10 Queues chart shows your ten largest queues by number of messages. Each bar is labelled with the recipient domain and the pool. Use the list at the top right of the chart to choose All pools or a single pool.

Top Queues table​

The table lists every queue that has mail in it, largest first:

ColumnWhat it shows
NameThe recipient domain the messages are waiting for, such as example.com
PoolThe pool the messages are being sent through. See Dedicated Pools.
RcptHow many messages are waiting
KBytesThe total size of the waiting messages
ConnHow many connections are open to that domain right now. 0 means Mumara ONE is waiting before its next try.
PausedYes if delivery to that domain has been paused, No otherwise
ModeHow the queue is being delivered: normal, or a slower backoff mode when the recipient's server has asked Mumara ONE to slow down
ActionsView last error (eye icon) and Delete queue (trash icon)

Use the list above the table to show All pools or one pool, and the length menu to show more rows.

View the last error​

Click the eye icon to open Last Error Received. It shows when the error happened and the exact reply the recipient's server gave the last time it deferred a message. For example:

Reply containsUsually means
421, "try again later", "rate limited", "too many connections"The provider is limiting how fast it accepts your mail. Mumara ONE slows down and keeps trying.
451, 452, "temporary failure", "insufficient system storage"A temporary problem on the recipient's side
"blocked", "reputation", "spam", a link to a provider's postmaster pageThe provider is deferring your mail because of your sending reputation or content
Connection or DNS errorsThe recipient's mail server can't be reached

Delete a queue​

Click the trash icon (Delete queue) and confirm when asked Are you sure?. You'll be warned: "once deleted, all emails inside this queue will be flushed."

Deleting a queue throws the messages away

Every message in the queue is removed and is not delivered. It isn't retried, and it doesn't come back. Use Delete queue only when you're sure those messages must not arrive, for example a campaign sent to the wrong list or to the wrong address. Never delete a queue to speed things up: a slow queue delivers on its own once the recipient's server accepts mail again.

What happens to waiting messages​

A message in a queue is retried automatically at intervals until one of these happens:

  • the recipient's server accepts it: it becomes Delivered
  • the recipient's server rejects it outright: it becomes Bounced
  • its retry time runs out: it bounces with the category message-expired. See Bounces.

The Delayed counter on the Summary counts messages that had to be retried.

When to worry​

Short queues that come and go are normal, especially:

  • during and shortly after a large campaign
  • at the big mailbox providers, which limit how fast they accept mail from each sender
  • when you're warming up new Dedicated IPs, which are deliberately sent slowly at first

Look closer when:

  • one domain's queue keeps growing instead of shrinking
  • a queue is still there hours later
  • the last error mentions a block, reputation or spam
  • Paused shows Yes

What to do:

  1. Read the Last Error Received. It usually says what the provider wants, and many include a link to the provider's postmaster page.
  2. Check your recent Bounce Rate and Complaint Rate on the Summary. Rising rates are the most common reason providers start deferring mail.
  3. Slow down your sending to that provider, and send only to your most engaged contacts until the queue clears.
  4. If the queue doesn't move for several hours, or you don't understand the error, contact Mumara support and include the queue name and the error text.

See Sending Reputation for how to recover a provider's trust.

Common questions​

A customer says they didn't get my email. Is it stuck in a queue?​

Look the message up in Delivery Logs by the recipient's address. A message still waiting shows the status Received. Then check the queue for the recipient's domain here.

Can I retry a queue now?​

No. Mumara ONE schedules the retries itself, and trying faster than the recipient's server allows only makes the deferrals last longer.

Why do the big mailbox providers have a queue during every campaign?​

They limit how many messages they accept from each sender at a time, so a large send always builds a short queue at each of them. As long as the queue shrinks and clears within a few hours, and the last error is about rate limiting rather than blocking, nothing is wrong.

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