SQL Server Replication across firewall We would like to set up replication between two SQL Server 2012 instances.  

Server "Internal" can see and make connections to server "External". External is completely firewalled from the internal network. No inbound connections are allowed on any port.  

We want to set up transactional replication from internal to external for a read-only copy on server External. When configuring External as the subscriber, it wants to connect to the publisher which it cannot do. 

All my searching leads me to articles on which ports to forward but that is not going to work for us. Basically what we want to do is have Internal initiate the connection and push updates to a copy on External. Up until now we have been using SSIS packages to push data but it's starting to border on unmanageable.
Are you able to set up a shared folder where only the SQL Service accounts have access? If so, since you are looking for a read-only subscriber, one option may be to use log shipping leaving the database in STANDBY. Of course, this is dependent on how often you need the data updated. Every time a log is restored, the users will be kicked off the secondary. Let's say every hour you restore a log backup, users will be kicked off during the restore, but the data will be pretty close to that time.