If you send emails via our SMTP servers (submission SMTP: smtp.mail.de), it may happen that our mail servers reject the delivery. Here you will find the most common error messages, including an explanation of why they occur and how you can fix the problem.
| Error message(s) | Reason / Solution |
|---|---|
| 535 5.7.8 Error: authentication failed: UGFzc3dvcmQ6 535 5.7.8 SASL LOGIN authentication failed: VXNlcm5hbWU6 535 5.7.8 SASL LOGIN authentication failed: UGFzc3dvcmQ6 535 5.7.8 SASL PLAIN authentication failed | If you receive one of these error messages, it means that either the username or the password is incorrect. Please check both and try again. |
| Connection timed out Server not responding | This error message means that you cannot reach our SMTP servers. This can have several reasons: - You made a typo when configuring the SMTP server. Please check the server name, port, and SSL/TLS settings. - Spam or a large number of failed login attempts were detected from your IP address. As a result, your IP address may have been temporarily blocked. Please check all your devices for correct login credentials. If you still receive the same error message after several hours, please contact us and include the error message and your current public IP address. |
| Connection refused Connection rejected | This error message means that you cannot reach our SMTP servers. In most cases, this is caused by a typo in the SMTP server configuration in your email program. Please check the server name, port, and SSL/TLS settings. |
| Your sender rate is over limits The number of emails per day is too high. | Your daily sending limit has been exceeded. Please wait before trying again. You can view your current sending limit in the webmail interface on the start page/dashboard in the "Account Information" widget. You can increase your sending limit by upgrading to a larger premium package. |
| Relay access denied | This error message means that our SMTP servers are not forwarding your email to the internet because you are not authenticated with the SMTP server. Without knowing who you are and which mailbox belongs to you, our server refuses to send the email. Please enable SMTP authentication and configure your correct username and password. |
| Recipient address rejected: Domain not found Recipient address rejected: need fully-qualified address | The recipient email address is invalid. Either it is not a complete valid address, or the domain (the part after the @ symbol) does not exist. Possibly a typo or a copy & paste error? |
| Sender address rejected: not owned by user | This error message occurs when you authenticate with your mailbox but try to send an email using a sender address that does not belong to you. Our SMTP servers check whether you are sending from one of your own email addresses (main address or alias) or from a foreign address. |
| spam id=xxxxxxx::xxxxxx-xxxxxxx-xxxxxxx/xx/xxxxxxx | The email was classified as spam and our server rejected the delivery. This often happens when you try to forward a spam email. Another possible reason is that your email contains a "malicious link" that our system detected as dangerous. Please check whether your email contains spam characteristics. If you believe that the spam classification is an error on our part (a so-called "false positive"), please contact us and include the spam ID, your sender email address, and the approximate time. We will gladly review and correct the classification if necessary. Thank you. |
| Message size exceeds fixed limit The email size exceeds the limit | Your email is too large to be sent. Depending on the selected email package, you can send emails up to 60 MB or 100 MB in size. Please note that attachments can become larger during transmission than they appear locally. This happens, for example, when they are converted to base64 format, which your email program does automatically. Another reason may be that the file size is displayed in MB. 1 MB is not 1,000,000 bytes, but 1,048,576 bytes. Solution: Reduce the size of the email by splitting attachments across two emails, or upload the attachment to online storage and send only a download link. |
| Error (0x800CCC78) Server response: 555 5.5.4 Unsupported option: SMTPUTF8 | This error code usually refers to an email address containing umlauts (ü, ö, ä, ß) that could not be sent. |
| Error (0x800ccc0e) in Outlook | The error code 0x800ccc0e in Outlook indicates that the server settings (server name, port, and transport encryption SSL/TLS/StartTLS) are missing or incorrectly configured. Please check the IMAP and SMTP server settings for our service. |
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