Ubuntu perfect server 16.04 LTS

Then I have no idea....

As mxtoolbox couldn't connect... are you sure you route port 25 to your postfix server? You said it's in DMZ but check again if port 25 is pointed elsewhere...

 

i will check this.

When i look in Ispconfig Monitor/Mail-error-log i see this
Dec 30 13:39:09 server amavis[2228]: (02228-02) (!!)TROUBLE in process_request: Error writing an SMTP response to the socket: Broken pipe at (eval 97) line 1346

Is this maybe the problem?

 

maybe... or try telnet on localhost to see if server listens to it or whatever happens:

http://articles.slicehost.com/2008/8/6/postfix-using-telnet-to-test-postfix

 

Yesterday suddenly everything's works, i can send and receive mail.
My wifi din't work so i do a update with...... sudo apt-get update and ......sudo apt-get dist-upgrade
After this i restarted my server, wifi works fine now, but now again i can not send and receive mails
What is going wrong. How to i solve this problem?

 

It seems that DNS is not properly configured

Code:

[lesca@dodo ~]$ telnet 87.209.2.17 25
Trying 87.209.2.17...
Connected to 87.209.2.17.
Escape character is '^]'.
220 server1.kutscher.nl ESMTP Postfix (Ubuntu)
quit
221 2.0.0 Bye
Connection closed by foreign host.

Ok, the port 25 is open and a server1 (your server?) is receptive

Code:

[lesca@dodo ~]$ host -tmx kutscher.nl
kutscher.nl mail is handled by 10 mail.kutscher.nl.
[lesca@dodo ~]$ host -ta mail.kutscher.nl
mail.kutscher.nl has address 87.209.2.17

Ok, the MX record is property configured ... but point to a host called "mail", this could be a problem...

Code:

[lesca@dodo ~]$ host 87.209.2.17
17.2.209.87.in-addr.arpa domain name pointer ip17-2-209-87.adsl2.static.versatel.nl.
[lesca@dodo ~]$ host -ttxt kutscher.nl
kutscher.nl has no TXT record

Not Ok, the PTR record not point to your server and there is not a SPF txt record

Try send a message to your server and post the log.
Hope this help
Dario