I just made a fresh install of XOOPS 2.6 in a new windows server and it does not send the activation key to the new members: I get these msg:

- When a new user try to register they get:
You are now registered. However, we were unable to send the activation mail to your email account due to an internal error that had occurred on our server. We are sorry for the inconvenience, please send the webmaster an email notifying him/her of the situation.
- When I try to send email to my users I get this
Errors
Could not instantiate mail()
Could not send mail to Cr.
Sending message completed.

Please, could you solve this problem?
Thanks.

Check you options in the System Administration>Preferences for you email setup options. Try using sendmail or PHPmail and make sure you have these configured on your syststem for proper mail handling.

got it.... thanks a lot.

got it.... thanks a lot.