can it send using wired?
what troubleshooting steps have you done?
Most probably the reason is it could not contact the smtp server that use for sending mail.
The ISP (which provide for an outgoing smtp server), but it is not always accessible from outside the isp. In that case it gave errors, check if the port 25 may be blocking…. u can tel netting to check this as: telnet <smtpservername> 25.