emails not sent

hi,
I use some forms on my website in order to send e-mails to my human resssources services.
I’ve seen, since a few times (but I don’t know when it’s beginning), that some emails where sent and I can’t find them in my submissions. In the opposite, i’ve got some submissions registered on wordpress with no emails sent.
These problems concern anly a few number of submissions, but I don’t know from where they come.
Do you have any ideas ?
Thanks
Best regards
Clément
PS : sorry for my bad bad english

The page I need help with: [log in to see the link]