The best time to register for DrupalCon Dublin is now. Earlybird discounts end July 29.
I can't send email because of this error
550 user cannot send email from scripts
please help me to solve this problem
This is not a Drupal problem but a server problem. You need to talk to your server manager or hosting company about it.
Drupal is a registered trademark of Dries Buytaert.