I've had the same problem myself. My best guesses as to why my domain has been dinged: 1) It's on a VPS, that IP may be flagged already 2) I often use a VPN,

I've had the same problem myself. My best guesses as to why my domain has been dinged: 1) It's on a VPS, that IP may be flagged already 2) I often use a VPN, and sometimes send emails out through my server using it. This probably raises the red flags. 3) It's a non-standard TLD, .co 4) I don't use any Google services with that email address/domain (I assume doing so adds some level of measurable trust) 5) I'm not in the address book of a lot of gmail users, because this is my private server, that I use only for job seeking, and personal communication. This has really done damage in the past. I've applied for jobs, and heard back weeks after they hired someone, letting me know, woops, I ended up in their spam folder. Trying to meet with a friend? I can't email them, I need to use Facebook or Gmail... welp. This is super annoying. I kind of understand why it happens, but it's just a little sad that building your own fort, so to speak, is so impossible. Things I tried to do to mitigate this: 1) Made my web domain https only (why not?) 2) set up DKIM and SPF (didn't seem to have any effect) 3) proper SMTP authentication, secure port only 4) Reached out to Google via the typical forms they offer, and heard nothing, obviously.