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not writing or contacting for a while; neglecting (failing) to write (call, visit, etc.); long silence
御無沙汰しておりますがお元気ですか。
It's been a while. How are you?
長らく御無沙汰して申し訳ありません。
I'm sorry for not being in touch for so long.
御無沙汰していた友人から連絡が来た。
I got a message from a friend I hadn't heard from.