Product/Software support. Above the Tier 1 level, at the stage where you're talking with the Dev team directly.

Developers don't want to talk to customers. So you need someone who can understand either the code or the developer's comments, but can then put it in layman's terms.

Edit: DevOps, too.

HR

We were a Linux System Administration consultancy. The product wasn't the e-mails, but nearly everything we did for our clients was designed/planned, scheduled, organized, and documented in e-mail. Yes, sometimes we would work on things with the client on the phone, those were usually followed up with an e-mail about what was done.

These e-mails were copied to our internal mailing lists so that they could be peer reviewed and someone else could be cross-trained on it in case the primary wasn't available. Also, every task we did had a one sentence description written up that would be shared with the team, again as a kind of peer review.

In my team, Duty Managers / Service Delivery Managers / Operations Managers. Communication in every which direction is #1 skillset I look for in the team (as well as being organized, disciplined, eager to learn, sense of ownership).

A lot of the job is talking to technical teams, talking to functional teams, talking to business teams, talking to management and executives; translate, summarize, liaison, co-ordinate, plan and inform. Customize medium, format, length, message for each group to enhance understanding. Develop spidey sense of paranoia against assumptions, misunderstandings.

Technical Account Management.

Recruitment

any customer facing job I guess. like sales, marketing, support, PR?