getAllBlockedEmailDomains() {
        let configBlocklist = this.config.get('spam:blocked_email_domains') || [];
        let settingsBlocklist = this.settingsCache.get('blocked_email_domains') || [];

        const normaliseDomains = domain => domain && domain.trim().toLowerCase().split('@').pop();
        const filterValidDomains = domain => domain && domain.includes('.');

        configBlocklist = Array.isArray(configBlocklist) ? configBlocklist.map(normaliseDomains).filter(filterValidDomains) : [];
        settingsBlocklist = Array.isArray(settingsBlocklist) ? settingsBlocklist.map(normaliseDomains).filter(filterValidDomains) : [];

        return Array.from(new Set([
            ...configBlocklist,
            ...settingsBlocklist
        ]));
    }
Generates an array of the blocked email domains from both config and settings
Normalizes the stored values by trimming, converting to lowercase and keeping only the email domain, e.g. 'hello@spam.xyz' -> 'spam.xyz'
Filters out domains without a dot
Returns an array of unique domains

@returns {string[]}