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Best email provider against spam?
(lemy.lol)
This is a most excellent place for technology news and articles.
Then my guess is that someone got ahold of that email list and started using it to send spam and that caused Gmails algorithm to start flagging anything sent out to a bunch of members of that email group at the same time as such.
Maybe someone spoofed the From field on some spam, using their email address. Thereby marking that From address as a spammer. I've seen this happen both ways.