Im getting this error when a new user registers.
Ther registration is succesfull. My guess is that the error is when the system tries to email the user about the registration. The exceptions says something about an unavailable mailbox and adress states the adress of the user that signed up. I know the email is correct cause its my own adress.
I have configured and tested the admin mail and host mail.

: DotNetNuke.Services.Exceptions.ModuleLoadException: Mailbox unavailable. The server response was: 5.7.1 ... Relaying denied. IP name lookup failed [206.123.116.178] ---> System.Net.Mail.SmtpFailedRecipientException: Mailbox unavailable. The server response was: 5.7.1 ... Relaying denied. IP name lookup failed [206.123.116.178] at System.Net.Mail.SmtpTransport.SendMail(MailAddress sender, MailAddressCollection recipients, String deliveryNotify, SmtpFailedRecipientException& exception) at System.Net.Mail.SmtpClient.Send(MailMessage message) at DotNetNuke.Services.Mail.Mail.SendEmail(String fromAddress, String senderAddress, String toAddress, String subject, String body) in C:\CCNet_Builds\CE_Development\WorkingDirectory\Library\Services\Mail\Mail.vb:line 420 at DotNetNuke.Services.Mail.Mail.SendMail(UserInfo user, MessageType msgType, PortalSettings settings) in C:\CCNet_Builds\CE_Development\WorkingDirectory\Library\Services\Mail\Mail.vb:line 103 at DotNetNuke.Entities.Modules.UserModuleBase.CompleteUserCreation(UserCreateStatus createStatus, UserInfo newUser, Boolean notify, Boolean register) in C:\CCNet_Builds\CE_Development\WorkingDirectory\Library\Entities\Modules\UserModuleBase.vb:line 485 at DotNetNuke.Modules.Admin.Users.ManageUsers.UserCreateCompleted(Object sender, UserCreatedEventArgs e) --- End of inner exception stack trace ---

The key in the error message is "Relaying denied."

This means that the SMTP server is not configured so that it will send mail from your DotNetNuke site to the user's address. I'd bet that your address -- the one to which it will send email -- is in the same domain as the site. In this case, the SMTP server will send the mail.

Check with whoever is responsible for the SMTP server. They should be able to configure it to meet your needs.

The mailserver is not on the same server as the dnn portal. Furthermore, when i configure the host email smtp and try the TEST function, it properly sends an email to that adress.

Should i still contact the mail provider?

It is the domain that counts, not which server hosts the mail server.

What is the domain of the web site?
What is the domain of the email address that works?
What is the domain of the address that fails?

Yes, if you contact the mail provider, give them that information, and also tell them that you got a "relaying denied" message for the failing address. They should be able to fix things for you quite quickly.

Website: SalsaAkadmien.se
AdminEmail: webmaster@SalsaAkademien.se

Users email: Is whatever the users put in, but in the exception above its Lautaro.Arino@gmail.com

Yes. The admin and the website are on the same domain, so there is not a relaying problem sending to the admin. The gmailmaddress requires sending out of the domain. That is why it is a problem if the mail server will not relay.

Im not really understanding what the problem is, but as you said before, i will contact my email provider.
What should i ask for?

If you show them the line in the error message about relaying, they will understand it.

Here is an explanation: http://www.gammadyne.com/relaying_denied.htm