Project url marked as spam by email host

HI - a weird one here, not sure if anyone will have seen this before.

I just signed up to Glitch earlier today, remixed a Heardle project, it seems to be working fine, so I emailed a copy to someone to have them test it out.

The email bounced straight back tome with the following message: “550 A URL in this email (jockrock-heardle . glitch . me) is listed on Please resolve and retry”

Now, I realise that the server is being a bit over-cautious or needs to have this whitelisted, but I’m a bit baffled as to how it could be believed to be spam so soon after it went live. Just thought I’d see if it had happened to anyone else. Thanks.

They seem to say:

If your message was wrongly blocked, please reach out via alternate means to the recipient and request that they release and train the message from their spam quarantine, and then request a delist. This will not only resolve the immediate reputation issue, but also helps in improving your IP/domain reputation for the future.

That means you need to contact them.