Accessing external hosts from docker container

I am trying to dockerize my application. I have two servers, say server1 and server2. Server1 uses webservice hosted on server2. I have this in my
/etc/default/docker on server1:

DOCKER_OPTS="--dns --dns --iptables=false" 

As I understand this prevents docker from making any changes to iptables, overriding UFW settings. The UFW status shows this:

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    To                         Action      From
    --                         ------      ----
    22                         ALLOW       Anywhere
    443                        ALLOW       Anywhere
    2375/tcp                   ALLOW       Anywhere
    22 (v6)                    ALLOW       Anywhere (v6)
    443 (v6)                   ALLOW       Anywhere (v6)
    2375/tcp (v6)              ALLOW       Anywhere (v6)

    Now the trouble is I am not able to access server2 from my app which runs
    in a container on server1. If I don’t use the –iptables=false flag then I can access server2. What can I do to access server2 from the container without having to sacrifice UFW ?

    If it matters , both server1 and server2 are on digitalocean and have private networking enabled.

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