Error sending E-mail Help

Hi people,

Something wierd is happening in my nopcommerce store. It's not sending e-mail and I could see in the registry that the e-mail From in used as E-mail To in the logs. So when I enter the E-mail queeu and invert the e-mails one by another, really inverting the system sends the message. The problem is that when customer enters into my contact page they inform their e-mail, but into the system their e-mail appers as the From one!! My version is 3.70 and it was deactivated, is used to work fine before, I activated it and now having such problem. Can you help me?

RE: "It's not sending e-mail "
Do you see any errors in the System > Log?

In your admin > email accounts, Edit the default email account, and do a TEST.  Does that work OK?

Here follows the Log message:

Short Message: Error sending e-mail. Mailbox unavailable. The server response was: From domain must match authenticated domain

Long Message: System.Net.Mail.SmtpException: Mailbox unavailable. The server response was: From domain must match authenticated domain at System.Net.Mail.MailCommand.CheckResponse(SmtpStatusCode statusCode, String response) at System.Net.Mail.MailCommand.Send(SmtpConnection conn, Byte[] command, MailAddress from, Boolean allowUnicode) at System.Net.Mail.SmtpTransport.SendMail(MailAddress sender, MailAddressCollection recipients, String deliveryNotify, Boolean allowUnicode, SmtpFailedRecipientException& exception) at System.Net.Mail.SmtpClient.Send(MailMessage message) at Nop.Services.Messages.EmailSender.SendEmail(EmailAccount emailAccount, String subject, String body, String fromAddress, String fromName, String toAddress, String toName, String replyTo, String replyToName, IEnumerable`1 bcc, IEnumerable`1 cc, String attachmentFilePath, String attachmentFileName, Int32 attachedDownloadId) at Nop.Services.Messages.QueuedMessagesSendTask.Execute()

When I see the message queue I can see the e-mail address is inverted, where to have e-mail to it has e-mail from and vice-versa.