Why is Gmail bouncing emails sent via Resend ("Blocked due to content")? Could it be my cheap domain?
I’m using Resend for a test project, and my emails to Gmail are bouncing with the error: "Blocked due to content: The message was rejected because it contained content that the recipient's server doesn't allow." I'm currently using a cheap/free domain for…
I’m using Resend for a test project, and my emails to Gmail are bouncing with the error: "Blocked due to content: The message was rejected because it contained content that the recipient's server doesn't allow." I'm currently using a cheap/free domain for testing. Since this is just a personal test project, I don’t want to buy a .com or .net domain if I don't have to. Could Gmail be blocking my emails simply because of the low-cost domain extension? If the domain is the issue, what is a good, cheap domain TLD that works reliably with Gmail and Resend for testing purposes?
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Interesting! I bought.app domain for 5 bucks, didn't have that problem.
Probably not the TLD directly - "blocked due to content" is Gmail's wording for content/pattern issues, not domain cost. Cheap TLDs do correlate with spam more broadly, but that's a different signal than this specific error. More likely cause: does the domain have SPF, DKIM, and DMARC set up? A brand-new domain with none of those configured is one of the most common reasons Gmail hard-blocks like this, regardless of TLD. I've set this up from scratch before (95%+ delivery once properly configured), worth checking those three records before switching domains, since a new domain without them will hit the same wall.
Gmail probably isn’t judging the TLD alone, but cheap/new domains get basically no benefit of the doubt. The usual suspects are SPF/DKIM/DMARC, domain age/reputation, link content, and whether the message looks like template sludge. For testing, I’d use a boring low-drama domain you can keep long term, set the auth records properly, and send extremely plain emails first. Deliverability is already annoying enough without making the domain look like it came from a vending machine.
It's a combination of things: you start with low reputation, so you have to have a very clean house in the beginning. I tried to get everything in order SPF/DMARC/etc (there are sites like https://dmarcly.com/tools/ that will check for you), but also check addresses before I send them emails (in case spambots register bogus emails), keep track of bounce rates, and build an email body that doesn't look generic (this tripped me once - and the fix was to have a differentiated subject line). My emails are all transactional, so that helps too. There's no quick path to sending emails reliably. Are you sending transactional or marketing emails?
Gmail is rejecting the message body, so the TLD price isn't the cause here. Send yourself the same email with every link and image stripped out and see whether it goes through. Add things back individually after that. A shortened link, a tracking domain that doesn't match your sending domain, or a link out to a brand new domain will each do it. Auth records matter and you should have all 3, but a missing SPF or DKIM gives you a different rejection than this.