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Mail server

Error messages you may receive from the e-mail server

Error messages can be returned when sending or receiving from an e-mail server. Since each e-mail server uses its own descriptions, different formulations can be used.


Mail server error description in the returned e-mail message.

You will receive an e-mail explaining why the e-mail message was rejected. 

Mail server returns error 421 Service not available....

The SMTP server is not able to resolve other domain names into IP addresses, because this service does not accept further requests.

This can mean the following:

There is a technical defect in the SMTP server. Only the provider can help here.

The SMPT server is overloaded by a high volume of e-mails. Please try to resend the e-mail later.

E-mail server - Error 4.7.1 Sender address rejected

The provider’s e-mail server replies “Error 4.7.1 Sender address rejected”, which means that your e-mail address is on a so-called blacklist. This means that sending your e-mails with your e-mail address is not allowed.
Blacklists are used by providers on the Internet to block spam or advertising mail. Your sender address may have been used by third parties to send spam mails.  For this reason it was put on the blacklist.
Contact the provider to clarify why your address is on this blacklist.

If a 500 or 501 syntax error message appears during e-mail reception.

Check the following input:

  • Is your e-mail address entered correctly.
  • Have you entered the name of your computer correctly. No spaces, special characters or umlauts may be used.

Under Windows 10:
To change the computer name, click System and Security under Control Panel, then click System. Under Computer Name / Settings for Computer Name, Domain and Workgroup, click on the “Change settings” link on the right.

A window will open. Here you click on the “Change” button and enter the computer name. Confirm your entries by clicking on the “OK” button

Error 501 invalid HELO arguments

Error 501 in the “Helo” of mail headers your “computer name” – also called “hostname” – is identified as your client name from which the mail is sent.  If there is a space in this “Helo”, this is considered an error on some mail servers. As a result, the error message “501 invalid HELO Arguments” is returned.
Aus diesem Grund ist in den Optionen von GcMail die Änderung des „Helo“ vorgesehen.
Under the menu Settings/Options/ under the link Send and Receive you can enter your own “Helo”. Make sure that the name you choose does not contain any spaces.

Error 530 Authentication required

The mail server issues the error 530 Authentication. Probably you did not activate SMTP authentication when you created the e-mail account. Go to the e-mail account settings and select the relevant e-mail account in the accounts list.
In the “Edit Account” window that opens, click the “Advanced Settings” button and under the “Outbox” tab. Please check the box “SMTP server requires authentication” and confirm your entry.

If you are not using GcMail follow the description of your software manufacturer.

Error 541 - E-Mail comes back with the

Here the recipient (or mail server) has refused to accept your e-mail.  The only thing that helps here is that your recipient adds your email address to his whitelist.

Error 550 Requested action not taken mailbox unavailable „E.g., mailbox not found, invalid domain, no Access“

This message is returned by the provider’s SMTP server if the recipient’s mailbox is invalid or does not exist.

Error message: : 550 cannot resolve your domain

Send a mail once to arthur@testmail.local and you get the same error message 550 cannot resolve.

Kurz gesagt
The e-mail address is incorrect.
Mailbox is unreachable.
The mail server does not consider the sending domain to be trustworthy.
Your own mail server will not send the message, for example if the email contains a virus.

Check whether the name of each address data has a comma between first name and surname, for example. Commas are used as separators between the individual mail addresses. If you want the comma to remain between first name and last name, set First name and last name in quotation marks.

Before:Liesel, Musterfrau (incorrect)
After: „Liesel, Musterfrau“ (correct)


Error: smtp; 550 5.7.1

Diagnostic-Code: Recipient address rejected: User temporary locked. Please try again

The message came back because the recipient is temporarily blocked. You are asked to try again later

550 Reject due to policy restrictions

The sending domain is listed as spam domain.

You can download from the website of Spam House check if your IP address or domain is listed If “Yes” you request the deletion of the entry.

Error smtp; 552 5.2.2 mailbox quota exceeded for this recipient

Recipient’s mailbox is full and can no longer receive messages. If necessary, inform the recipient of this here or try to send the message again at a later time.

Error 552 Requested mail action abortedexceeded storage allocation

The recipient’s mailbox is full and can no longer store email messages. Stop sending the e-mail and try again later.

Transmission error:5.7.0 (mp025) Need to authenticate via SMTP-AUTH-Login

Your mail server requires a special login for sending e-mails. You must activate the following in the account settings on the “Server” tab: „SMTP server requires authentication.“

Socket-Error 10061

This message can have the following causes:

GcMail Mail connects to a port (server port) that is blocked. If GcMail now tries to send a message, port 25/587 is blocked. The port 110/995 POP3 is blocked when retrieving e-mails and 143/993 for IMAP.

The mail server returns the message “Socket-Error 10061 Connection refused”.

You should check the following:

  • Check the entries for the POP3/IMAP account and the SMTP entries for sending.
  • Check if you are connected to the Internet.
  • Check if your virus program does not block our program!

If everything is entered correctly and the receiving and sending still does not work. Should you ever completely deactivate your antivirus program or remove our e-mail program from the real-time scanner. The same applies to e-mail programs of other manufacturers.

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