There are many digital marketing courses available online, and they can vary in terms of content, length, and cost. Some popular options include:

1. The Digital Marketing Specialization on Coursera: This is a series of six courses that cover the fundamentals of digital marketing, including search engine optimization (SEO), social media marketing, and email marketing. The course is offered by the University of Illinois at Urbana-Champaign and is taught by experienced marketing professionals.

2. The Digital Marketing Institute: This is a professional organization that offers a variety of digital marketing courses and certifications, including the Digital Marketing Professional Diploma and the Digital Marketing Executive Course.

3. Google Digital Garage: This is a free online course that covers the basics of digital marketing and is offered by Google. The course covers topics such as online marketing, website optimization, and measuring success.

4. Hubspot Academy: This online learning platform offers free digital marketing, sales, and service courses on Inbound, Content Marketing, Email Marketing, Growth-Driven Design and more, all under one roof.

5. The Complete Digital Marketing Course by Udemy: This is a comprehensive course that covers a wide range of digital marketing topics, including SEO, PPC, social media marketing, and email marketing. The course includes over 20 hours of video content and is taught by experienced marketers.

It's always a good idea to research the different options and read reviews from past students to determine which course may be the best fit for you. Many courses offer certifications on completion which can help to enhance your credibility and credibility in the industry.

Also, since the field of Digital Marketing is very dynamic and ever-evolving, I would recommend that you keep learning and upskilling over time to stay updated with latest trends and developments.