A domain name can cost as little as £10, similarly most email services cost ~£5-£15 per person per month. Its normally pretty easy to link a domain to an email provider and doesn't cost anything other than time.
If a company can't be bothered to implement the most basic online branding people will make their assumptions and some will filter your company out because of it. With the cost to implement so low (e.g. £160 per year), even the loss/gain of a single customer would justify it.