Solve a "bogus HELO" error

This guide details the message error "bogus HELO" to allow you to avoid it.

When and why this mistake?

To make it simple, the SMTP protocol (for sending e-mails) has several phases, the first of which is for the sender to announce who it is through a command called HELO and which must be followed by a valid address.

If you receive errors mentioning bogus HELO it is that parameters (used by the person trying to write to you or by the software you are trying to use) do not conform to the RFC (item 4.1.1.1) This avoids the spread of viruses and spam.

Infomaniak refuses e.g. any message from a mail server that would be called "server" instead of having a full name of type "serveur.domain.xyz" (= FQDN, "Fully Qualified Domain Name" or "fully named host name"). Nor can an IP address simply define the server. Examples of rejection:

The remote server email service has not been configured with a valid FQDN:

220 mta-gw1.infomaniak.ch ESMTP Infomaniak Network Mail Servers;HELO 127.0.0.1 

or the mail server is not configured to use a real FQDN:

220 mta-gw1.infomaniak.ch ESMTP Infomaniak Network Mail Servers;HELO [127.0.0.1] 

or the mail server is not configured to use a real FQDN:

220 mta-gw1.infomaniak.ch ESMTP Infomaniak Network Mail Servers;HELO localhost 

or the mail server returns a host that is not in canonical form (FQDN):

220 mta-gw1.infomaniak.ch ESMTP Infomaniak Network Mail Servers;HELO www 

where it is in a list of banned HELO at Infomaniak:

220 mta-gw1.infomaniak.ch ESMTP Infomaniak Network Mail Servers;HELO fakedomain.xyz

This will always result in an error:

250 mta-gw1.infomaniak.ch Hello, pleased to meet you
MAIL FROM: user123@infomaniak.ch
250 2.1.0 user123@infomaniak.ch... Sender ok
RCPT TO: user123@infomaniak.ch
550 5.7.1 user123@infomaniak.ch... Access denied - bogus HELO [1] …

Check the configuration of your email server so that it uses a correct HELO parameter when establishing the SMTP connection.