Blocked Or Rejected Email – Error 550 Explained

Sep 4, 2019

All email services at Skystra are on our email hosting platform. There are no blacklists or rejected emails. However, if you do come across that error when using another service, here’s what you can do.

What Does Error 550 Mean?

Let’s say you send an email and all of a sudden see one of the following two messages:

“550 Blocked Error”
“550 Requested action not taken: mailbox unavailable”

This means your email has bounced, i.e. the server where your recipient’s email account resides has sent the email right back to you.

Put in plain English – your email didn’t send and it’s time to take action!

Domain Blacklisting

There may be several reasons as to why your email is bouncing, but most often this is due to your email domain being blacklisted.

Your email domain is the part after the @ sign. If for example, your email is [email protected], your email domain would be

Domain blacklisting can occur if your email domain has started sending out spam or if your website has malware.

The recipient’s spam filter or security layer would detect this and automatically flag and send your email back to you, i.e. blacklisting it.

A quick way to see if your email domain has been blacklisted is by going to MXToolBox, type in your email domain and hit Blacklist Check:

If you see your email domain blacklisted, you can contact the lister and request to be taken off and you’ll go through a protocol to whitelist (essentially, unblock) your email domain so you can send emails to your recipient.

At Skystra, your account, including website & email data, rest on a proactive security layer, so your data is always safe and sound!

That said, it’s always good to be proactive and below are 5 troubleshooting tips to avoid Error 550’s and rejected emails altogether :-)!

5 Tips To Avoid Error 550

1. Double-check the recipient’s email address for spelling, punctuation, or spacing. Sometimes emails bounce because of a simple misspelling or putting a .ca instead of .com.

2. Run a malware scan on your computer and make sure to have an active malware and anti-virus software installed on your computer which automatically scans and runs reports.

3. Set strong email passwords that are long, include a mix of lower & upper case letters, and a mix of special characters. Also, get into the habit of changing your passwords on a regular basis and using a password manager.

4. Keep your software and applications up to date and remember, if you’re on the Skystra Cloud, we do this automatically for you!

5. Be wary of Apps and websites that request access to your contact list as this may be a sneaky way for spammers to get access to your email data and that of your contacts!