taesonssI am taught that never start a sentence with "but" and "so", they are only put in middle of a sentence.
That is an antiquated rule that some old-fashioned English grammarians invented in the Victorian age of the 19th century, and it kind of stuck.
It is completely acceptable to begin a sentence with one of the FANBOYS conjunctions. Many famous English writers do it.
https://www.grammar-monster.com/lessons/starting_a_sentence_with_and_or_but.htm
Comments
They only tell you that because beginners do it far too often if you tell them it's OK.
It can be. It's a judgment call. It seems OK this time because the sentence starts to drag a bit just where they end it, and they get a running start on the next one with "so". But (there's one) this is not exemplary writing. For example, they say there are five domains, and then they list six.
It is best avoided in formal writing. It has a casual air.