Truth be told, internal customers have far more ability to make you miserable. A poor relationship with an internal customer can cause ripple effects that echo out throughout the whole organization, drawing in upper management into frays. That's always a bad thing. That's one reason why it's so important to build those internal customer relationships. Here's a few things to consider.
- An internal customer who is angry and upset with you has access to others in the organization, where externals don't. That means that if the issue is important enough to that person, he's likely to escalate his complaint up the management chain. This is something you don't want. Not only does that make you look bad in the eyes of your bosses, but senior managers absolutely HATE to have to mediate or intervene in conflicts lower down in the hierarchy. And often, they'll come back to you to express their annoyance.
- In many organizations there often exist silos of information, where one department doesn't communicate with other departments. There's often a lack of understanding of the policies and procedures on one department when it comes to providing services to an external customer. When you have repeated conflicts and disagreements with internal customers, you make it MORE likely that the internal customer will "go around you", or avoid dealing with you as much as possible. That can create even worse silos, and interfere with the mission of the business. Problems with internal customers should be seen as opportunities to break through the communication barriers internally, which is why it's so important to build long term relationships.
- Believe it or not conflicts between one entity and its internal customer can eventually evolve into a state of siege or war, where each department is at each other's throat. It can be exceedingly toxic, and create lots of dysfunctional activity that eats up huge time, and creates huge amounts of stress.