Email notifications stopped

I have installed since last year Norton Family. Actual version installed is 2.6.0.52. The OS is Windows XP Pro SP3. I noted that during last 4 or 5 weeks no email was generated by NOF. NOF regularly generates alerts, but it doesn't send any email.

I have:

1) Checked email address configured

2) Checked type of notifications sent on Settings/Notify part of NOF site

3) Added a second email address

4) Checked in Spam folder of both email

 

Any ideas to restore email sending?

 

Many thanks in advance, Enzo.