Boost your domain's credibility – how do you set up an SPF record correctly?

Imagine you own an accounting firm and, along with it, an internet domain that hosts your website – for example www.dobreucetnictvi.cz. You routinely write to your clients from the e-mail address janek@dobreucetnictvi.cz, and you discuss everything important with them by e-mail. Your clients trust you, the firm has a good name and your domain has an excellent reputation on the internet. But what if someone abuses it to trick your customers into handing over sensitive data? And how do you prevent that?