From WHMCS Documentation

General Settings

The General Settings page is where you change the vast majority of WHMCS general settings. Below is a description of each tab of the general config to aid in finding what you need.

• General - this is where basic settings such as your company name, address, domain and template are configured
• Localisation - from here you can configure country, language and currency settings
• Ordering - for configuring TOS URL, where the user is taken to at the end of the order process and other order specific settings
• Domains - this is where you configure domain registration options and pricing for domain addons
• Mail - where you can choose the method used to send mail and set sending preferences and the default signature
• Support - allowing you to customise the order ticket replies are displayed and the allowed attachment types
• Invoices - from here you can set all invoicing/payment related settings
• Credit - this is where you enable/disable the credit funding feature in the client area and set limits
• Affiliates - this is where the affiliate system settings are configured such as required payout level, bonus deposit and default commission percentage
• Other - this tab contains all the miscellaneous options which don't fit under other headings

Email Sending Protocol

WHMCS can use either PHP Mail or SMTP for the sending of emails. SMTP has the benefit of being less likely to be judged to be spam but it does have lower performance than the PHP Mail option. You can select the method you wish to use in General Settings > Mail. For SMTP, you must enter the login details for a valid SMTP account.

Automation Settings

The automation settings configuration page is where you configure all the automated events such as automated suspension, unsuspension, termination, how far in advance to generate invoices, when overdue notices are sent, etc... It's the one central place that controls everything that the cron does during it's daily run. All the options should be fairly self explanitory and each one has a description explaining it to guide you through exactly what it is/does.