Question Error-Mails produced by subscriptions

if you put a look on my initial-posting, the screenshot-1 with this strange message of "Could not instantiate mail function" - could this be a trace to the mal-function ?

This error come from a misconfigured mail setting, but you have said that it works with others components if you can look into php error log or mail error log maybe you will see a related error message

An other usage of automatic mails is the "private message" function - and this function works perfectly, included the announcement-mails.
The mail to confirm registration of users to well, too.

For the php-error-log and mail-error-log I just asked the Webmaster - I'm only responsable for the Kunena-extension.
He's looking where he could find these logs ...

I just received from the Webmaster 2 files :
a huge access log 5,7 MB containing things like

[13/Mar/2015:17:33:46 +0100] "GET /media/kunena/attachments/818/Lemberg.jpg HTTP/1.1" 304 - " www.seniorbern.ch/index.php/forum/foto-f...r-ein-ort-der-stille " "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2272.89 Safari/537.36" www.seniorbern.ch
92.104.125.195 - - [13/Mar/2015:17:33:46 +0100] "GET /media/kunena/attachments/818/Lemberg1.jpg HTTP/1.1" 304 - " www.seniorbern.ch/index.php/forum/foto-f...r-ein-ort-der-stille " "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2272.89 Safari/537.36" www.seniorbern.ch
92.104.125.195 - - [13/Mar/2015:17:34:01 +0100] "GET /index.php/forum/aktuell HTTP/1.1" 200 22626 "-" "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2272.89 Safari/537.36" www.seniorbern.ch
92.104.125.195 - - [13/Mar/2015:17:34:02 +0100] "GET /plugins/system/jcemediabox/themes/standard/popup.html HTTP/1.1" 304 - " www.seniorbern.ch/index.php/forum/aktuell " "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2272.89 Safari/537.36" www.seniorbern.ch
92.104.125.195 - - [13/Mar/2015:17:34:02 +0100] "GET /plugins/system/jcemediabox/themes/standard/tooltip.html HTTP/1.1" 304 - " www.seniorbern.ch/index.php/forum/aktuell " "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2272.89 Safari/537.36" www.seniorbern.ch
194.150.244.94 - - [13/Mar/2015:17:34:17 +0100] "GET /media/kunena/avatars/resized/size144/users/avatar669.jpg HTTP/1.1" 304 - "-" "Mozilla/4.0 (compatible;)" www.seniorbern.ch

and an error-log of 400 KB with things like
INFO 85.0.109.106 cookiefailure Ein leeres Passwort ist nicht zulässig (empty password not allowed)

but no mail-log found

waiting for better news, but still nothing ....
I'm sad having hundreds of error mails every day.

Should I better disable the whole subscriptions-feature ?

could you check if you can send a mail with the [email protected] account, maybe the account is blocked by your hoster

The mail function is working correctly for real existing subscriptions.

The problem here is the fact, that the system try to send a subscription-mail for every posting written in the whole forum-system, regardless if a subscription exists or not.

If one or more subscriptions for a thread exist really, the mail will have an TO-address and will be correctly sent.
If there ist no subscription, the mail will be sent anyway, but without a TO-adress - and this is the reason for all these error-mails.