Ghost automatically sends new members a confirmation email after signup, to confirm their membership to your publication. The confirmation button can be configured to link to a custom welcome page after confirming signup. Read more about setting up custom welcome pages.
Ghost can also be integrated with several other tools via Zapier, or using the Admin API, to send emails to new members.
For example, you could setup a "zap" using Zapier, to add new members to a custom list with a tool like Drip, or ConvertKit. This would allow you to send custom welcome emails, or setup a custom email campaign for new members.