ThinkReservations sends transactional emails to your guests throughout their guest journey with you. Over time, this can add up to a large number of emails being sent from your ThinkReservations account to your guests. If there is a problem delivering an email, we will send a notification email to you.
Example Email
Our example email is broken up in the gray boxes, with explanations below each section:
Subject: [Action Required] An email was not delivered due to a bounce
The subject will be the same, and the from address will always be one of those two senders. This allows you to set up rules or filters in your email system so that you can set up a process to deal with these emails when they come in.
An email was not delivered due to a bounce.
At January 1, 2026 12:23:45 PM, an email was sent from examplehotel@yourinn.com with the subject Sean, your stay at The Viewpoint Hotel. The email was not delivered due to the reasons found below:
The first part of the email tells you 3 important pieces of information:
The date and time that the email was sent out.
Who the sender was (usually your property, but sometimes ThinkReservations)
The subject line of the email that was attempted
Note that the address that actually failed appears further down.
Tip: If your subject lines are not unique, you can add personalized variables to include details like the customer's name or their confirmation ID!
Bounce Type: Permanent
Bounce SubType: General
Bounce Description: ThinkReservations received a general hard bounce and recommends that you remove the recipient's email address from your mailing list.
The next section tells you if the issue is something that might be solved on its own, or if it's just a bad email address altogether.
Bounce Type: This will be either transient or permanent. Transient means that the error message is temporary, such as their inbox being full. Permanent means it's an issue with the address itself, such as an email address that doesn't actually exist. You'll occasionally see Undetermined, which means the guest's email provider rejected the message but didn't say why. No subtype will be present when "Undetermined".
Bounce SubType: This narrows things down to the specific reason. The ones you're most likely to see:
Permanent
General – The address doesn't exist. This is almost always a typo taken over the phone, but it could also be something like a work address that was shut off after the guest booked.
Suppressed – This address is on a do-not-send list, so the message wasn't attempted. Usually, that's because it hard bounced recently, but it can also happen if someone marked a previous ThinkReservations email as spam. Contact us to have an address removed.
NoEmail – The bounce came back without a usable address attached. Rare.
Transient
MailboxFull – The guest's inbox is over its storage limit. Common with old accounts that don't get cleaned out.
MessageTooLarge – The email and its attachments were bigger than their provider allows.
ContentRejected – Their spam or content filter blocked the message. Corporate and government email systems are usually the culprit.
AttachmentRejected – Their provider wouldn't accept the attachment. Same story: locked-down work email.
General – A temporary problem the provider didn't explain, like their mail server being down or overloaded. Unfortunately, somewhat common.
Bounce Description: A plain-English version of the two fields above, plus what we recommend doing about it. In the example above, "general hard bounce" is just another way of saying permanent + general: the address isn't real, resending won't fix it, and it should come out of your guest records.
Bounced Email Addresses:
emailwithatypo@gmail.com [smtp; 550-5.1.1 The email account that you tried to reach does not exist. Please try double-checking the recipient's email address for typos or unnecessary spaces. For more information, go to https://support.google.com/mail/?p=NoSuchUser - gsmtp]
This last section is arguably the most important. It tells you exactly which email address(es) are not being sent, and the technical details as to why. While the section above gives you a high-level answer, this section is helpful when trying to troubleshoot. In the above example, the two critical pieces are:
emailwithatypo@gmail.com - the email address being sent to.
"The email account that you tried to reach does not exist" - the error
It is possible that your own email address is the problematic recipient address! ThinkReservations sends emails to you when the BCC email feature is turned on in Business Settings.
If one of your staff accidentally clicks to mark an email from ThinkReservations as SPAM, those emails will stop being delivered, citing an issue with the email address being on the suppression list.
Please contact us so our technical team can review and remove your email from our suppression list.
What to do next
So, after reviewing this email, you should know when the email was sent, to what address, and with what subject line. The bounce subtype and description, along with the technical details, should tell you what to do next.
In some transient bounce cases, the system will attempt to resend the email on your behalf, and the bounce back message is triggered only after the system has given up. This is why you may notice the notification is sent several days after the email was originally attempted.
You will want to work with the guest and get the correct information. Search for that email address in ThinkReservations > Customers, and update it. Use the Advanced Search if needed. When you have updated the email address, manually resend the emails to your guest.