Everyone comes to the community from a different background. Many committers contribute as part of their employment, if their employer uses ASF software. Some committers are consultants, who keep up on technology and build custom solutions for various customers. Some committers are students or hobbyists, who do it for their own personal reasons.
For individuals who make a living from software or related endeavours, it’s important to disclose your affiliations when you join a community; not doing so is considered rude. It’s not necessary to announce it loudly or constantly, but you should make sure that the community knows who you work for if part of your ASF contribution is done for your employer.
Your choice of email address is not as important; plenty of contributors use their personal emails when working on an employer’s project. If your employer specifically is advocating for a change within a project, it’s a good idea if you include a disclaimer at the end of your email letting the community know.