expression
Polite expression of gratitude, more emphatic than ありがとうございます. The どうも adds a sense of 'very much' or 'truly'.
お土産をいただき、どうもありがとうございます。
Thank you very much for the souvenir.
ご親切にどうもありがとうございます。
Thank you very much for your kindness.
Standard polite 'thank you'; less emphatic than どうもありがとうございます.
Casual 'thanks' or 'very'; can be used alone as a brief thank you, but どうもありがとうございます is more polite and complete.
Combination of どうも (very, truly) and ありがとうございます (polite thank you). ありがとう originates from 有り難し (difficult to exist, rare), expressing gratitude for something rare or precious.