The inexistent PTR-record is a completely different problem.
Certs don't work magically. You have to install them but I think you don't really understand what we want you to do.
Why it's strange that lets encrypt is not creating a cert for postfix?
Or is it just me that imagining things and the error that comes up is a mirrage ?
If you want continue to receive help from us, you should refrain a bit 
You're confusing many things here.
The SSL certificates generated by the i-MSCP LetsEncrypt plugin have nothing to do with the SSL certificate used by the mail services (postfix, dovecot, courier...).
The SSL certificate for the mail services is generated independantly during the i-MSCP installation or its reconfiguration. Currently, there is only one shared SSL certificate for the following services:
You can reconfigure that SSL certificate by running the following command:
then you'll be asked for your SSL certificate. If you choose the self-signed option, your mail client will say that the certificate is not valid. If you choose your own SSL certificate, you must be sure that the common name matches your server hostname (hostname -f). Also, when you will setup your mail client, you must use the same hostname.
Why it's strange that lets encrypt is not creating a cert for postfix?
Thats not what i am saying and i understand that its not created for postfix
Thats why i am puzzeled that outlook is using that cert
Display MoreIf you want continue to receive help from us, you should refrain a bit
The SSL certificates generated by the i-MSCP LetsEncrypt plugin have nothing to do with the SSL certificate used by the mail services (postfix, dovecot, courier...).
The SSL certificate for the mail services is generated independantly during the i-MSCP installation or its reconfiguration. Currently, there is only one shared SSL certificate for the following services:
- Postfix (SMTP),
- Dovecot or Courier (IMAP, POP)
- ProFTPD or vsftpd (FTP)
You can reconfigure that SSL certificate by running the following command:
then you'll be asked for your SSL certificate. If you choose the self-signed option, your mail client will say that the certificate is not valid. If you choose your own SSL certificate, you must be sure that the common name matches your server hostname (hostname -f). Also, when you will setup your mail client, you must use the same hostname.
I dont need a seperate certificate for postfix as i understand it should work fine with the shared SSL certificate
I can use the fqdn for outlook because i have the domain with wildcards so i can use dummy.nl with wildcard serv2 what will result in serv1.dummy.nl
If i use that for outlook then i have another error wich is the helo
etc/hostname is:
serv2
etc/ host is:
213.xxx.xxx.18 serv2.dummy.nl serv2
::ffff:213.xxx.xxx.18 serv2.dummy.nl serv2
hostname -f is : serv2.dummy.nl
So what i am thinking is when the reverse dns/ptr/fqdn is ready that it should work
Its only crappy that i have to make this request for the ptr/reverse dns/fqdn at the isp and that takes time before its done.
@Nuxwin
If you want continue to receive help from us, you should refrain a bit 
You're confusing many things here.
I understand here we say Babelonian speech confusion
We all speak differant languages and english is not our native language so its hard to explain but also hard to understand.
Then given the fact that its not my cup of tea but all hobby for me its even harder to understand. For you guys its all very simple because its your thing and you study for it. But give me a hammer and a screwdriver and i will build you a house thats my thing.
And dont get me wrong i really respect the things you guys do and the magic you create with your fingertips is amazing and i would really love to get your work working for me aswell and i know it should otherwise you would not have created it and there are many who have it working 110%.
My other server works 110% with another pannel but there is litle developement there so thats why i am switching now
So what i am thinking is when the reverse dns/ptr/fqdn is ready that it should work
As we have said to you X times already, your problem has nothing to do with the reverse DNS (PTR)... Whatever. You are too stubborn.
If i use that for outlook then i have another error wich is the helo
Which error exactly. You should provide us the full (exact) error message.
I dont need a seperate certificate for postfix as i understand it should work fine with the shared SSL certificate
Yes, this is totally right.
When connecting to your server via openssl s_client -showcerts -connect aruba-auto-verhuur.nl:465 the result says that you cert is self-signed and has no wildcard.
If you really have a valid cert, please run the command that already has been provided to you to install it.
edit: When connecting to your panel (i.e. Port 4443) the cert is also self-signed.
Which error exactly. You should provide us the full (exact) error message.
Test-e-mailbericht verzenden: De reactie van de server was: 504 5.5.2 <mijn>: Helo command
this is the error i get when i use the serv2.dummy.nl
incoming mail = mail.serv2.dummy.nl
outgoing mail = mail.serv2.dummy.nl
As you mentioned: The PTR record is currently not correctly set. Please wait for your server provider's answer of your request to change it.
edit: This Website could help you afterwards: https://www.mail-tester.com/
