Are you trying to send an email proposal, and all of a sudden, you receive an email that states the following?
“501 5.1.3 Bad recipient address syntax” or “501 5.1.3 Invalid recipient address.”
Don’t worry; it is a common email error called SMTP Email Error 501 5.1.3, which often occurs when there is an issue with the recipient’s email address format. More specifically, this happens if you input an incorrect email address format, whether it is due to the omission of essential components or the addition of unauthorized character(s).
When this happens it is impossible for your emails to be retrieved by your recipient. Fortunately, this blog post will help you uncover a deeper understanding of this error, and the various ways on how to fix it.
Imagine you are back in the old days when electronic mails hadn’t been invented yet. You sent a letter to someone but included the wrong address, or perhaps an incorrect name. The courier would most likely return your letter, or at worst, throw it in the trash.
The same principle applies to SMTP Email Error 501 5.1.3. It signals specific issues with the email-sending process, often related to syntax or protocol violations, indicating that the recipient’s email address is incorrectly formatted.
These errors can occur due to a missing ‘@’ symbol, an incomplete domain, or an incorrect arrangement of characters. Encountering this error prevents the email from reaching the intended recipient, halting communication and delaying the transmission of crucial information.
In a business environment, Error 501 5.1.3 can have significant repercussions, such as the disruption of operations, adverse effects on customer service, and potentially missed deadlines or opportunities.
For individual users, this error can mean a failure to communicate effectively with contacts, which can be especially problematic if the sender is awaiting an important personal email, such as job applications, university admissions, or medical appointments.
Furthermore, recurrent SMTP errors can negatively impact the sender’s reputation with email servers, potentially causing emails to be blocked or filtered into spam folders more frequently.
So, what can be the reason for this error message? SMTP Email Error 501 5.1.3 is not limited to incorrect email formatting — although it is the most common culprit.
This is the most direct cause of the 501 5.1.3 error. When an email address is formatted incorrectly; for example, forgetting to insert the “@” symbol, including spaces and different characters that are absent from the user email address.
It can also be a simple typo error, such as a “.” Instead of a “.” or a switched character. For example, [email protected] instead of [email protected].
Sometimes, the error stemmed from an imperfect email configuration, or when the settings required to send, receive, or synchronize emails are either incorrect or incomplete.
For example, if the email client is set up with incorrect SMTP server details or authentication parameters, it may cause issues with how the address fields are handled.
Usage of automated systems such as apps, or website notification systems can result in programming errors, generating incorrect email addresses for emails that are not correctly formatted.
For instance, an automated script could merge the user’s name and details into the email address in a manner that differs from the normal email format.
Another issue is email aliases and complex forwarding rules.
The principle of email aliases is for a company to utilize a different domain name that represents the name of the company. Every email sent to these email aliases are forwarded to the main email domain.
SMTP Errors arise if there is an issue with an email system in an organization that uses configurable email aliases or a complicated forwarding system, the addresses generated this way can be unintended and might not be valid in the standard email format.
On the server side, if there are misconfigurations in how it is handling or validating email addresses, the 501 5.1.3 error might also occur. It includes mistakes in server rules dictating to a server how to handle an address or custom scripts editing an email header or address.
- Verify the recipient’s email address. Your recipient’s email address may have a typo or it is an incorrect format. It should have an ‘@’ and the proper domain name. For instance, [email protected]
- Confirm your SMTP Settings and Set it up Properly. Confirm that your SMTP settings are correctly configured in your email client:
- SMTP Server Address: smtp.gmail.com
- Use Authentication: yes
- Secure Connection: TLS/SSL based on your mail client/website SMTP plugin
- SMTP Username: your Gmail account ([email protected])
- SMTP Password: your Gmail password
- Gmail SMTP port: 465 (SSL) or 587 (TLS)
To setup your Gmail’s SMTP. You can use the following:
- Google Workspace SMTP Relay Service/
- Gmail’s SMTP Server
- Restricted Gmail SMTP Server.
3. Check Extensions and Add-ons. Some browser extensions prevent Gmail from working correctly. Disable them in your Gmail by accessing it through a different browser to see if the error is resolved, or use an incognito browser.
- Email Address Validation. Double-check the email address of your recipient for errors. Outlook can sometimes autofill addresses incorrectly, so it’s worth verifying.
- Update Your Outlook. Make sure you are using the latest version of Outlook, as older versions might have compatibility issues with current SMTP standards.
- Review Account Settings. Go to File -> Account Settings -> Server Settings and ensure the following:
- Outgoing mail server (SMTP): smtp.office365.com
- Port: 587
- Encryption Method: STARTTLS
- Authentication: Your Outlook email and password
- Check Recipient Address. Like with other platforms, ensure the recipient’s email address is correct and properly formatted without extra spaces or characters.
- SMTP Configuration. Ensure your email is using Yahoo Mail appropriately and set it with the right SMTP settings:
- SMTP Server: smtp.mail.yahoo.com
- Port: 465 (SSL required) or 587 (TLS)
- Username: [Your full Yahoo email address]
- Password: [Your Yahoo password]
- Secure Connection. Make sure that SSL/TLS encryption is enabled for the outgoing mail server to secure your emails and comply with Yahoo’s requirements.
Warmy.io provides email warm-up services and deliverability support, a vital tool for maintaining a positive reputation and ensures that your emails get to the recipients as intended.
Warmy.io’s warm-up services serve to gently ramp up the amount of emails a new or a long-inactive sender may send. It helps preserve the sender’s reputation and avoid flagging them as spammers — sudden spikes in sent messages can activate spam filters and SMTP servers may interpret significant changes in email volume as a sign of suspicious activity.
Warmy.io’s email checking services offers a free email deliverability test which allows you to check how your emails are being treated by various email services.
Tests from the free email deliverability test can help identify potential problems before an error occurs.
For instance, the test may identify that the user’s email is blacklisted, which can mark the email as spam.
Lastly, SPF and DMARC record generators, sets up accurate SPF and DMARC is critical as it verifies that the emails sent from your domain are genuine.
Warmy.io provides tools to generate these records for free. Properly configured SPF and DMARC enhances email security as the system will not send the email to a receiver if the receiver cannot verify the authenticity of the emails. In addition to this security, the domain’s reputation can be safe from being used as a front for spam.
Emails are a vital part of your professional and personal life. Ensuring that you have proper email formats and user configurations helps avoid miscommunication and complications in your activities.
Prompt management of SMTP errors can guarantee the correct sending of emails. However, just like in the traditional method of sending mail, ensuring that you have the correct address and name guarantees that it will be received by the correct recipient; and in the form of sending emails, avoids encountering the 501 5.1.3 error.
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