My company has a customer who constantly uses the wrong alias (e.g., jsmith instead of smith@domain.com) when he sends an email message to a certain person in our domain. The customer wants us to add a proxy address for the recipient, but I'm hesitant about making that change. What's the best practice?

You pose an interesting question. On the one hand, adding a proxy address for a recipient is easy, and you'd gain some brownie points with that customer if you did so. On the other hand, the customer's request is akin to asking the phone company to add an extra phone number to a phone line to help the one person who chronically misdials it. More important, adding a proxy address doesn't solve the real problem and increases (albeit slightly) the administrators' workload.

Perhaps looking at the bigger picture can help you solve this dilemma. Do the benefits of having a consistent address space outweigh the benefits of having a satisfied customer? In this case, I recommend adding the proxy address—it's easy to do, requires little additional work, and adds convenience for the customer at minimal cost to you.