What’s Causing the 550 SMTP Error and How lớn Fix It?
Estimated reading time: 10 minutes
It’s always frustrating lớn see your beautiful gmail campaigns failing due lớn gmail delivery issues. The causes of such failures range from suspicious elements in the email’s nội dung, incorrect DNS records, invalid gmail addresses lớn gmail quotas, recipient’s restrictions, and gmail server issues. The good news is that the majority of the issues can be fixed by the sender.
Below we’ll dive into the explanation of the most significant SMTP errors 550. What’s causing them? How tự you fix them? Read on lớn learn that now.
What Does the 550 SMTP Error Mean?
The SMTP error code of 550 indicates that the gmail message has been rejected by the recipient’s mail server. It is important lớn note that the 550 codes indicate a permanent delivery failure meaning that the server will not re-attempt lớn deliver a message.
In such a scenario, the recipient’s server typically returns the message lớn the sender including a bounce notice with the error code and mô tả tìm kiếm. These can help senders understand the cause of rejection in order they can solve the issue before re-trying the delivery.
550 Thư điện tử Error Types and Causes
There are different types of the 550 gmail error depending on the issue that caused the delivery failure. Below are the most common types of the error of 550:
Email Error: 550 High Probability of Spam
The reason this error notice displays is that either the recipient’s mail server has categorized the message as spam because of the issues with the sending IP or domain name, or a portion of the gmail includes nội dung that triggered spam filters. Usually, spam filters look for warning signs like:
1. Suspicious content
The following elements may trigger spam filters and lead lớn the gmail rejection due lớn a high probability of spam:
- missing unsubscribe link;
- text or Subject line written in ALL CAPS;
- terminology used in emails reported as spam;
- URLs lớn dubious online sources;
- URLs containing blacklisted domains;
- suspicious attachments;
- invalid HTML code.
2. Blacklisted IP Address or Domain
RBLs (Realtime Blackhole Lists) are lists of IP addresses or domain name names that are known lớn produce spam or host malware that sends or forwards spam emails. The receiving server can reject your gmail with the “550 High Probability of Spam” SMTP error if the IP address or domain name your gmail originates from is listed in RBL.
3. Unauthorized Sender
The recipient’s server performs a DNS lookup lớn verify if the sending IP address has been authorized by the domain name owner lớn send emails on behalf of the domain name. The server looks at the SPF record lớn tự that verification. If the SPF authentication fails, the server can reject the gmail returning the “550 High Probability of Spam” SMTP error.
The most common causes of an unsuccessful SPF authentication test include:
– failure lớn include the sender in the SPF record;
– failure lớn comply with the 10-DNS lookup limit;
– incorrect SPF record syntax;
– multiple SPF records published in DNS.
4. Invalid DKIM Signature
To verify the integrity of the message, the recipient’s server looks at the DKIM signature. It uses the private and public keys lớn decrypt the signature and ensure the message wasn’t altered in transmission. In case of an unsuccessful DKIM verification, the message can be rejected with the “550 High Probability of Spam” delivery error.
Typically a DKIM verification fails when:
- the message was changed while hoping from server lớn server;
- the private key or public key is invalid;
- the DKIM record syntax is invalid;
- the DKIM signature is missing.
5. Failed DMARC Authentication
DMARC stands for Domain-Based Message Authentication, Reporting, and Conformance and allows the recipient’s mail server lớn verify the authenticity of the sender and the integrity of the message based on SPF and DKIM.
In order for the DMARC lớn pass, the domain name used in Header From must align with either the domain name used in Mail FROM or with the domain name used in the DKIM signature. When both SPF alignment and DKIM alignment fail, the message is considered lớn have been sent from an illegal source and can be returned with the “550 High Probability of Spam” SMTP delivery error.
Email Error: 550 This Message was Classified as Spam and May not Be Delivered
This 550 error indicates that something in the gmail nội dung or the way it was sent triggered the recipient’s spam filter. Typically, an gmail is rejected with this error if it has a lot of features of a spam message including the terminology, design, and HTML code. Additionally, sending the gmail using a Microsoft Outlook tài khoản without the SMTP authentication enabled will result in the gmail rejection with the 550 error.
Email Error: 550 5.7.0 Message Size Violation
This indicates that the size of the sent message exceeds the size that is allowed by the recipient. Attachments and embedded pictures increase the message size significantly. For security reasons in order lớn protect users from viruses and malware, the restrictions may be mix at the recipient’s mail server lớn block gmail messages with the size that exceeds the defined value.
Email Error: 550 Denied by Policy
This delivery error happens when emails sent lớn randomly created addresses are blocked by gmail security software, preventing attackers from guessing gmail addresses.
Email Error: 550 Blocked
The “550 Blocked” SMTP error, which typically comes with a bounce message, can be brought on by a number of things, such as
- improperly configured DNS settings;
- bad reputation of the sender’s IP or domain;
- user reported spam;
- email limit exceeded;
- recipient’s security solutions lượt thích spam filters and firewalls.
Email Error: 550 #5.1.0 Address Rejected
This error message indicates that the recipient’s server won’t accept emails from you. In most cases, this happens when the recipient blocks your gmail address.
Email Error: 550 #5.1.0 Sender Rejected
The cause of this error is similar lớn the one explained above. The message is rejected because the recipient’s mail server doesn’t accept the messages from the given sender. This happens when the sender’s gmail address or the domain name or the IP address is on the custom recipient’s blocklist.
Email Error: 550 Access Denied
This error message indicates that the gmail was rejected due lớn either security policies used at the recipient’s side or incorrect configuration on the sender’s side.
Email Error: 550 Authentication is Required for Relay
This means the SMTP authentication is not enabled. To send outgoing emails, you need lớn enable Simple Mail Transfer Protocol (SMTP) authentication in your gmail client.
Email Error: 550 Relay Not Permitted
The recipient’s server is not configured lớn accept the messages sent from the server you used.
How lớn Fix 550 SMTP Errors
The examination of the most common causes of the 550 SMTP error demonstrates that the majority of the 550 SMTP errors happen because of the issues residing on the sender’s side.
Therefore, it’s important that you verify your gmail sending process, setup, and gmail messages lớn fix or avoid getting the emails returned with the 550 error. In particular, here are the steps lớn take:
1. Optimize Your Message
To ensure the delivery of your gmail communications, you’ll want lớn take these important things into tài khoản when you design an HTML email:
- keep a good text-to-image ratio (60% vs 40%);
- use a correct HTML code;
- use URLs on trusted domains;
- avoid using ALL CAPS in the Subject line or body;
- avoid sending suspicious or large attachments;
- avoid sending messages of a big size;
- include an unsubscribe links.
2. Remove Your IP Address or Domain from Blacklists
Getting your dedicated IP address or sending domain name delisted and fixing the root cause of the listing is a good start. Find the URL lớn request removal from the list by visiting the RBL that listed your IP address or gmail domain name.
RBLs usually include details lượt thích the time of listing and the reason your IP or domain name was recorded. You can utilize this information lớn determine the reason for the blacklisting.
Your domain name or IP address might not be removed from the list for a few hours after the delisting request is submitted. But be aware that in the sự kiện of another instance of spam abuse, your IP address or domain name will be relisted. Therefore, figuring out and resolving the blacklisting’s root cause is the first action lớn take.
4. Properly Configure DNS Records
As invalid or missing gmail authentication records are a typical cause of the 550 SMTP error, you’ll want lớn verify your domain name settings especially if you have recently changed the gmail service provider.
Ensure the domain’s SPF record includes your legitimate sources and complies with the 10-DNS lookup limit. In case you need lớn exceed this limit, consider using a flattened SPF record lớn avoid SPF authentication failures.
Verify that the DKIM authentication is enabled for your messages in your gmail service provider.
Publish a valid DMARC record for your domain name. It’s important lớn have the gmail addresses for receiving DMARC reports in the record as they give insightful information about the gmail traffic and gmail authentication outcomes.
5. Check If Your Account Has Been Compromised
Even if you did everything right, you can still receive a 550 error notice. This may occur as a result of improper usage of your gmail tài khoản by a hacker or spammer.
Examine your Sent Items, paying particular attention lớn recent correspondence, lớn see if your tài khoản has been compromised. Have you sent any unusual or mysterious messages that you are not sure about?
Check your computer for malware and viruses and change your password if you discover that your gmail tài khoản has been compromised. Before sending another gmail, let your gmail administrator know so sánh they can unlock the tài khoản because the spammer might have changed additional settings in your mailbox.
6. Limit the Number of Emails
Internet service providers keep track of how many emails a domain name sends out each day. If you send too many emails, spam filters and other security tools may mark your gmail communications as spam.
The majority of gmail service providers impose the daily limitations for outbound emails. It’s recommended lớn not come close lớn the limit. Otherwise, you run rẩy the risk of harming your domain’s reputation with your ESP and other providers.
7. Verify Your SMTP Configuration
Without SMTP (Simple Mail Transfer Protocol), which mail servers utilize lớn transmit outgoing emails from the sender lớn the recipient, sending an gmail would not be possible. An SMTP protocol is a mix of guidelines that permits information sharing between various gmail accounts and applications.
The majority of gmail programs mix up SMTP automatically. Thư điện tử issues, however, may arise if the SMTP server requires a sender’s authentication. You may need lớn manually enable the SMTP authentication and enter your username and password lớn authenticate your tài khoản with the SMTP server in your gmail application.
Additionally, you may need lớn configure other settings such as allow your sending IP address or domain name with the SMTP server in order the server can accept connections from your IP or domain name.
8. Improve Your Sender Reputation
If after ensuring your message is optimized and sending infrastructure is mix up properly, you are still seeing the 550 SMTP error, the reason behind this error could be a bad sending reputation. ISPs look at various things lớn calculate your sending reputation: sent gmail volume, domain name age, bounce ratio, user complaint ratio, filtered emails, emails sent lớn Spam, user engagement etc.
It’s recommended that you stop sending emails from the domain name or IP until the 550 delivery error is resolved. If you are in the middle of an outreach chiến dịch, change the sender’s domain name or IP right away. Take the steps lớn improve your sending reputation by doing an inbox warmup, good list management, segmentation, re-activation campaigns etc.
Conclusion
Email marketing is effective, but it has its challenges. If you can identify the root causes of the gmail issues, understand the solutions, and are ready lớn put those solutions into practice, you’re well on your way lớn success. By following the definitive guide above, you can quickly resolve the 550 gmail error message.
Additionally, we encourage that you conduct deliverability testing. This will showcase gmail deliverability issues you may have with the ISPs and help you optimize and improve your outreach emails for a better Inbox placement rate.