I am attempting to transfer a deployment to another user, and we are both on the hobby plan. The transferee never receives the email to accept the transfer.

Their email log shows the following smtp 550 error, and not clear what to do about this.

> Event: failure error
> User: [redacted]
> Domain: hmbyc.org
> From Address: postmaster@cio79999.notify.railway.app
> Sender: [redacted]@hmbyc.org
> Sent Time: Jun 26, 2025, 2:34:14 PM
> Sender Host: pc233-26.mailgun.net
> Sender IP: 143.55.233.26
> Authentication: forwarder
> Spam Score: 0.8
> Recipient: [redacted]@hmbyc.org
> Delivery User: -system-
> Delivery Domain:
> Delivered To:
> Router: smarthostregular > Transport: remotesmtpsmartregular
> Out Time: Jun 26, 2025, 2:34:14 PM
> ID: 1uUuEl-00000000070-3Kjy
> Delivery Host: smtp.antispamcloud.com
> Delivery IP: 38.71.16.245
> Size: 21.09 KB
> Result: AES128-GCM-SHA256:128 CV=yes: SMTP error from remote mail server after MAIL FROM: SIZE=23216: 550-Verification failed for \n550-Called: 34.149.236.64\n550-Sent: RCPT TO:\n550-Response: 550 5.0.1 Recipient rejected\n550 Invalid sender

What can we do to resolve this, or is there a way to transfer ownership that does not involve email?

Thanks