Some users don't recieve weekly summary

Thank you for your concern @ToddZ
My instance is on Digital Ocean and the mails are sent via DreamHost SMTP (where I’ve the domain, DNS..). Someone tell me it’s not a good solution, others says it’s OK with a little private community (less than 500) and not many interactions
Discourse is regularely update (at least every week).
From this morning the things seems better (why?). I’m monitoring and I’ve the feeling that things are getting back to normal.
I’m monitoring