used for saying that a remark is not relevant to the main subject of your conversation. The abbreviation BTW is often used in electronic messages. 顺便提一下(缩写BTW常用于电子信息中)
By the way, Jeff called this afternoon and he wants you to call him back. 顺便说一句,杰夫今天下午来过电话,他要你给他回电话。