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Troubleshoot undelivered discussion emails
Troubleshoot undelivered discussion emails

Common error messages that you might see when we can’t deliver a discussion email.

Matthew James Finkel avatar
Written by Matthew James Finkel
Updated over a week ago

When we’re having trouble delivering a discussion email to a participant, we add a message to the discussion thread in Current RMS to let you know. 

The message tells you the email address that we couldn’t reach and provides some details about what might have happened. In most cases, we post the technical information that we receive from our mail server or the mail server of the recipient.

Email is an open format, but it’s often implemented in slightly different ways by mail servers and providers. This means that the error messages we get back aren’t always standard. For example, a message that we receive for the same error might be different for someone using Microsoft Exchange to someone using Google’s Gmail.

Here’s a list of common messages and some tips on how to resolve. Keep in mind that this list isn’t exhaustive and some of the error messages or codes might be slightly different.

Not delivering to previously bounced address.
The response received was: 605.

When we try to deliver an email and it doesn’t get through, it’s called “bouncing” because the email bounces back to us. When an email bounces, we’ll stop trying to send and suppress further delivery attempts.

High bounce rates negatively impact our sender reputation, which makes it less likely that discussion emails sent from Current will be delivered successfully. Temporarily suppressing delivery attempts to invalid email addresses protects our sending reputation.

To resolve:

  • check that the recipient’s email address exists and is correct

  • if possible, determine if there are any problems with the recipient’s email account

  • if you’re sure the problem has been resolved, use the “Check email suppression” action on the page in People & Organizations to delete the entry on our suppressions list

Recipient not known.
Mailbox unavailable.
User unknown in relay recipient table.
No such mailbox.
The response received was: 550 or
The response received as: 602

Messages like this usually indicate that domain (the part after the @ sign) is valid, but the email address isn’t correct.

To resolve:

  • check for spelling mistakes in the email address

  • if possible, check to see if the email address exists, e.g. by checking the company’s website

  • attempt to send from your own email inbox

  • send to another email address at the company

Rule imposed mailbox access for email address refused.
Recipient address rejected: Access denied.
Message rejected because `` is blacklisted.
The response received was: 550.

This kind of message generally means that the recipient’s mail server has blocked our messages. This could be because that they’ve been mistakenly marked as spam or caught by an email filter.

You’ve probably experienced this yourself, where legitimate messages have found their way into your spam folder. Automatic email spam filters can sometimes be over-eager and may mistakenly filter messages based on things like the language used, number of attachments, and time sent. 

To resolve: 

  • contact the recipient to let them know that this was filtered in error

  • if in regular contact, ask the recipient to add  to the trusted sender list or email whitelist

If we ever discover that our mail server has been placed on a blacklist, we take steps to contact the blacklist owner to have it removed.

No MX for email address
Unable to connect to MX servers
The response received was: 498 or
The response received was: 612.

Messages that make reference to “MX” usually mean that there’s a problem with how your recipient’s email servers are set up. 

If you’re familiar with running a website, you’ll know that you need to make sure that you’ve set up MX records and your mail servers are working OK in order to receive emails. A message like this suggests that the person you’re emailing is having problems with their configuration.

To resolve:

  • check that the email domain (the part after the @ sign) is correct

  • contact the recipient by another means to let them know you’ve having trouble emailing them

  • try again later – it could be a temporary problem

The response received was: 499
The response received was: 432

Response codes 499 or 432 with no other information are sometimes returned by Microsoft Exchange email servers. This could be because the recipient’s email queue has been stopped or their inbox has been temporarily frozen while an administrator works on their account.

To resolve:

  • contact the recipient by another means to let them know you’ve having trouble emailing them

  • try again later – it could be a temporary problem

The bounce description was: Email rejected due to security policies - link
Your message looks like SPAM or has been reported as SPAM - see link
The response received was: 554.

If you receive a message that includes a link to a security policy, blacklist, or spam filter, it sounds like our emails might have been blacklisted by a particular email provider or ISP. 

This is rare but can happen when emails are accidentally marked as spam by automated systems or by folk who move messages to spam in error.

We monitor these kind of responses and work with providers to make sure that we’re removed from these lists as quickly as possible. 

To resolve:

  • if in regular contact, ask the recipient to remove  from their spam filter

  • contact our Customer Success team using the green help bubble 

  • attempt to send from your own email inbox

If we’re ever blacklisted by a larger email provider, we’ll make an announcement on our status page and keep you posted on our progress.

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