Exim as a client, self signed cert on server?

I have exim server 1 which is at home on a residential DHCP address, and exim server 2 which is in a data centre on a fixed IP address.

I would like exim server 1 to forward all emails to exim server 2 which will them send them on to the recipients email servers.

It isn't working, and the only clue that I can see is in the logs on server2
2016-04-06 10:54:32 TLS client disconnected cleanly (rejected our certificate?)

server2 is listening on port 465 and is using a self signed cert

is this the problem? how do I get server 1 to accept a self signed cert?

server 1 seems to have two versions of exim which I don't understand
[root@mail /usr/local/etc/exim]# pkg_info |grep exim
exim-4.80.1_2       High performance MTA for Unix systems on the Internet
exim-4.82           High performance MTA for Unix systems on the Internet
and is running FreeBSD 8.4-RELEASE-p8

server 2 is running exim-4.80.1_2 on FreeBSD 9.3-RELEASE-p30

If I connect a gui client like Thunderbird direct to server 2 it works fine, although it does have to be told to accept the certificate.

I suppose the only other thing I can do is configure the home firewall to redirect all tcp 465 connections from the old server 1 to server 2.