Re: Outgoing emails listed as spam
Perhaps some of the words you use in your replies are spammy, i.e., words commonly used in spam mails, and so Gmail, etc. marked your mails as spam. But this is unlikely as you are responding to e-mails sent to you, and not soliciting proactively.
If you suspect this, do a search on spam trigger words, and see if you use any of these words.
Given that you are not on blacklists, I have to ask: how do you know that Gmail, etc. are marking your mails as spam? Sometimes people claim that mails went to spam folder to get out of responding immediately. Could this be the case? (I don't mean to offend you or your friends, just exploring all possibilities.)