NetExtender displays the error, “Sending can’t be completed in 10 seconds” for some One-Time Password connection attempts. This synchronization issue can cause a small SSL VPN IP address pool to become exhausted.Occurs when One-Time Password is enabled and the SMTP mail server causes a delay delivering the message, so that the OTP password is not received before it times out.
You can increase the timeout period to compensate for delay in SMTP by editing the advanced diagnostics setting in Sonicwall. To do so, log in to your Sonicwall device as admin.
After you have logged in, change the URL to /diag.html immediately proceeding the device IP address or FQDN. For example:
This will display the Sonicwall diagnostic. Scroll down to the log settings and change the SMTP Read Timeout value to the desired time in order to allow your SMTP server ample time to send the OTP password.