I see way too many market leaders on the list - just because they have a free plan doesn't mean they are good "for companies on a budget". The free tiers are designed to hook you in, but switching once you hit the limits can be very expensive (resource wise) and shouldn't be part of cost-saving strategy.

Take MailChimp for example - it's a very expensive email marketing solution.

BigMailer.io is a great alternative to EmailOctopus because it supports transactional emails (EmailOctopus doesn't) in addition to bulk and auto/drip, and it offers a more generous free tier - up to 5,000 contacts.