MailChannels common mail bounce back errors

MailChannels common mail bounce back errors

MailChannels is a privately held anti-spam technology company based in Vancouver, British Columbia. MailChannels specializes in software and services that block and detect spam sending, phishing and other abuse emails. MailChannels are a leader in blocking spam and abuse email within sending networks and services such as ISPs and web hosting providers.

1) 550 5.7.1 [SS] error

The 550 5.7.1 [SS] error indicates that the subject of the message contained spam like keywords that are commonly used for abuse or unsolicited email. The 5.xx nature of the response code refers that this was a permanent failure of your message and your message were returned due to high spam content. Perform the following ways to secure your account:

1) Change your email account password and also make sure that your new password has a minimum length of eight characters and uses a mixture of upper and lower-case characters, special characters and numbers.

2) Check your PC is secure and update your antivirus software and conduct a full scan of your system.

3) Make a delist request.

4) If the above step does not resolve this problem, please contact or from  submit a Fales positive report with a copy of the bounce back message.


2) 550 5.7.1 [CS] Message blocked error

If you are getting this error, it means the bounce back email is detected as a spam message.  If your legitimate email is blocked and included in the non-delivery report you received from your mail server when an email is bounced. You can submit a false positive report to MailChannels and the mail channels corrects its behaviour so that similar messages will not be blocked in future.

Please contact or from   submit a Fales positive report with the following details:

Sender email address

Authenticated username of the sender

Recipient email address

Error message


3) 550 5.7.1 [RBL] Sender blocked <IP or domain> error

If you are receiving this error, it means your server IP or domain is currently listed as a high-volume spam content by a reputable global blacklist. You need to check your domain is blacklisted in the domain lookup tool, If the domain is not blacklisted then check your server IP is blacklisted using

If the domain is blacklisted:

1) Make sure that the owner of the domain is using the domain for fraudulent or spamming purposes,

2) Change your control panel and email account password. Please check your password has a minimum length of eight characters and a mixture of upper and lower characters, special characters and numbers.

3) After completing the above steps, make a delist request of the domain from the domain lookup tool.

If the server IP is blacklisted:

Open a support ticket to


4) 550 5.7.1 [FBL] error

If you are getting a bounce back message with this error, it means that your email recipient has directly complained about email from your IP address account so the Mail Channels automatically block senders who receive complaints. If you receive this type of bounce back message from MailChannels, the email recipients frequently complain about your legitimate messages. Please follow the below steps:

1) Only send the email messages that recipients could reasonably expect to receive.

2) Avoid sending messages to recipients after many months of zero contacts.

3) Keep the communication of your recipients is clear.

4) Provide unsubscribe links prominently at the top and bottom of each message.


5) 550 5.7.1 [IRR] error

This error indicates that the email account has been blocked because the account has been sending messages to a large number of invalid email addresses. In this situation, you need to check and clean your mailing list, remove invalid mail addresses. You can use websites such as or for address verification.


If you need any further help, please do reach our support department.