The PHP mail knows a concern since the system updates made today. Some clients informed us already.
It is disturbing we understood... but at same time this is not a surprise because php mail is announced for 2 years as being dead process method.
Let's see if we can come back re-authorize
Meanwhile, if you want to use email, this is how to do forever, and it works perfectly :
https://support.yoorshop.hosting/knowledgebase/1119/Send-emails-via-smtp-from-your-site-not-with-phpmail-.html
News at 18h01 :
Le phpmail is working again, this was due to the much updates that happened today. Anyway, you must use smtp because this is the one which maximizes your deliverability !