many thanks for hint. Just the first point from the link above helped

I checked the Error & Issues sheet and found there was an error "the function wp_mail() is not working".

Therefore I contacted my hosting provider and problem was in the limit of messages to be sent per day, which was quite a low one. They have increased the limit and now everything seems to work correctly

Best Regards

Milan

Please start by checking these points one by one and leave some feedback for each point: https://wpforo.com/community/faq/not-receiving-automatic-replynotificationconfirmation-emails/#post-5344

all forum users are suddenly receiving the error message when entering new post "unable to send subscription mail". What could be a root cause please?

post is added to forum, just the confirmation mail is not sent.

thank you

Milan