arpReach version 1.1.023 and higher allows people whose domain's email is managed by Gmail to have bounces and incoming emailed subscriptions processed by arpReach.
This was not possible before version 1.1.023 because Gmail requires that you connect to it with SSL encryption and arpReach did not have that facility then.
The parameters Gmail specifies for connection by IMAP and POP3 are as follows:
IMAP SSL
Port: 993
Host: imap.gmail.com
POP3 SSL
Port: 995
Host: pop.gmail.com
Important note: IMAP or POP needs to be enabled in the settings of your Gmail account. This is done on the Forwarding and POP/IMAP tab of the settings screen in Gmail.
arpReach 1.1.023 (and higher) can connect to Gmail as above and it needs to do so on the ports shown. However, many web hosts' firewalls block outgoing connections on ports 993 and 995, so your web host needs to unblock outgoing connections on those ports before arpReach will be able to connect to it.
You can do it via your WHM/cPanel or by logging in to your server via SSH and editing the csf.conf file. For example, below is a link with instructions on how to do it when on Liquid Web:
https://www.liquidweb.com/kb/opening-ports-in-your-firewall/
If you are not comfortable doing it on your own, your web host should be able to do it for you.