hi ter you all
before we begin am dyslexia so spelling and grammar is a issue for me i’m trying my best so thanks in advance for your understanding of the situations 
i have got a very strange issue with the email configuration that i can’t seems to fix even with help form the iRedMail developer can seen to find the solution and we a running out of ideas
serario
nextcloud vm
os ubuntu 18.04 lts
nextcloud ver 18.0.3
ip addr 10.10.50.133/26
mailserver vm
os ubuntu 18.04 lts
running iRedMail ver 0.9.9
ip addr 10.10.50.13/26
on two different subnet but on the same vmhostserver
nextcloud mail config
‘mail_smtphost’ => ‘mail.bogers.solutions’,
‘mail_smtpauthtype’ => ‘LOGIN’,
‘mail_smtpauth’ => 1,
‘mail_smtpname’ => ‘robot@aactz.nl’,
‘mail_smtppassword’ => ‘…’,
‘mail_smtpport’ => ‘587’,
‘mail_smtpsecure’ => ‘tls’,
The config has been checked by the dev and needs to work. Before we hosted our own mail server we used a 3 party mail provider and the mail worked then. As of the network and firewall everything has been tested win10 vm with mail client with the same account details as the servera and on the same subnet. And that works the vm doesn’t have firewalls of their own
the error
A problem occurred while sending the email. Please revise your settings. (Error: Unable to connect with TLS encryption)
it can connect to the server via tls and the server has a signed cert form Sectigo. tested via
openssl s_client -connect mail.bogers.solutions:587 -starttls smtp