|Question:||You always wrote by e-mail.|
|Term:||Where is the "do"?|
|Lesson:||EnglishLingQ - Who Is She?, Part 10|
And You're welcome!!!!!!
"You always wrote by email?" is a statement made into a question (by changing the tone), which means the speaker is asking someone to confirm their suspicion.
"Did you always write by email?" is simply asking the same question, but without the speaker adding their own assumption.
Both are suitable in formal and informal situations.