Running on my Ubuntu Server I have
Openvpn Server + Pihole Dns (routing only dns)
& an iredmail server

I have a domain name which I have pointed to the server, and a fqdn is set

Everything works separately unless I wish to connect to this server via the domain name (for example the web address of the online mailbox) with a client already connected via OpenVPN - Im getting connection refused errors.

eg.
Connecting to openvpn server using domain in openvpn client config works ✔

connecting to ssh works using domain ✔

connecting to online mail inbox using domain works ✔

when connected to vpn,

all work when connecting via server's public ip address ✔

but refuse connection when using domain.

Im assuming its an firewall/iptables issue but im headdesking rn.

here are my iptables rules (ive combined rules of iredmail and pihole)

*filter
:INPUT DROP [0:0]
:FORWARD DROP [0:0]
:OUTPUT ACCEPT [0:0]

# Keep state.
-A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT

# Loop device.
-A INPUT -i lo -j ACCEPT

# Allow PING from remote hosts.
-A INPUT -p icmp --icmp-type echo-request -j ACCEPT

# ssh
-A INPUT -p tcp --dport 27 -j ACCEPT

# http, https
-A INPUT -p tcp --dport 80 -j ACCEPT
-A INPUT -p tcp --dport 443 -j ACCEPT

# smtp, submission
-A INPUT -p tcp --dport 25 -j ACCEPT
-A INPUT -p tcp --dport 587 -j ACCEPT

# pop3, pop3s
-A INPUT -p tcp --dport 110 -j ACCEPT
-A INPUT -p tcp --dport 995 -j ACCEPT
#-A INPUT -p tcp --dport 10110 -j ACCEPT

# imap, imaps
-A INPUT -p tcp --dport 143 -j ACCEPT
-A INPUT -p tcp --dport 993 -j ACCEPT
#-A INPUT -p tcp --dport 10143 -j ACCEPT

# lmtp
#-A INPUT -p tcp --dport 24 -j ACCEPT
#-A INPUT -p tcp --dport 1024 -j ACCEPT

# managesieve
#-A INPUT -p tcp --dport 4190 -j ACCEPT
#-A INPUT -p tcp --dport 10419 -j ACCEPT

# Dovecot SASL AUTH service for HAProxy
#-A INPUT -p tcp --dport 12346 -j ACCEPT

# ldap/ldaps
#-A INPUT -p tcp --dport 389 -j ACCEPT
#-A INPUT -p tcp --dport 636 -j ACCEPT


#-A INPUT -p tcp --dport 3306 -j ACCEPT
#-A INPUT -p tcp --dport 4444 -j ACCEPT
#-A INPUT -p tcp --dport 4567 -j ACCEPT
#-A INPUT -p tcp --dport 4568 -j ACCEPT

# PostgreSQL service.
#-A INPUT -p tcp --dport 5432 -j ACCEPT

# Amavisd
#-A INPUT -p tcp --dport 10024 -j ACCEPT
#-A INPUT -p tcp --dport 10025 -j ACCEPT
#-A INPUT -p tcp --dport 10026 -j ACCEPT
#-A INPUT -p tcp --dport 9998 -j ACCEPT

# iRedAPD
#-A INPUT -p tcp --dport 7777 -j ACCEPT

# ftp.
#-A INPUT -p tcp --dport 20 -j ACCEPT
#-A INPUT -p tcp --dport 21 -j ACCEPT

# ejabberd
#-A INPUT -p tcp --dport 5222 -j ACCEPT
#-A INPUT -p tcp --dport 5223 -j ACCEPT
#-A INPUT -p tcp --dport 5280 -j ACCEPT

-I INPUT -i tun0 -j ACCEPT

-A INPUT -i tun0 -p tcp --destination-port 53 -j ACCEPT
-A INPUT -i tun0 -p udp --destination-port 53 -j ACCEPT
-A INPUT -i tun0 -p tcp --destination-port 80 -j ACCEPT

-A INPUT -p tcp --destination-port 27 -j ACCEPT
-A INPUT -p tcp --destination-port 1194 -j ACCEPT
-A INPUT -p udp --destination-port 1194 -j ACCEPT

-I INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT

-I INPUT -i lo -j ACCEPT

#-A INPUT -p udp --dport 80 -j REJECT --reject-with icmp-port-unreachable
#-A INPUT -p tcp --dport 443 -j REJECT --reject-with tcp-reset
#-A INPUT -p udp --dport 443 -j REJECT --reject-with icmp-port-unreachable
COMMIT

and the result of ip routes

default via 192.168.1.1 dev enp2s1 proto static
10.8.0.0/24 dev tun0 proto kernel scope link src 10.8.0.1
192.168.1.0/24 dev enp2s1 proto kernel scope link src 192.168.1.200