Actually I think it is more likely to happen with an e-mail you receive daily than an e-mail you received only once unless the sender's address has been blacklisted.
A few years ago I had a problem with my e-mail that had been blacklisted and then I found out that I shouldn't be e-mailing my co-workers daily with multiple destinations on the "To" field. I should have been using the CC field.
If I had done it once or twice it would be ok but since I had been doing that daily, several times a day, I got blacklisted by Google.
Nabble staff. We never ask for passwords.