It should take no longer than sending any other email, if the email settings are correctly defined. Have you confirmed that any other type of emails from the system can be sent?
3CX can be set up to send a number of types of emails. One type is an alert if certain events happen, hacking, all trunks busy, and the like. If you enable some of these messages, and an event happens that should trigger one, and you don't receive it, then you may need to review your email (send) settings. If you change the sending email setting to that of another email account, one you receive email on, just fr a test, and an email is rejected by your email provider, you will receive a rejection notification. You might also want to check the Activity Log to see if there are any error messages associated with the sending of the emails.
You can also try implementing gmail to see if that works...
all set means that i received a message says "SMTP Test OK - your PBX can send emails">>> but when i select send welcome message i receive nothing,, firewall is off
Are you trying , repeatedly, to one email? If so, try changing the destination email address (for the extension), to another address for testing. See if it shows up there. If it does, then it may be a problem with the destination you are sending to.