MailTender gives you a live test inbox for email authentication. Send a message from whatever system you're trying to debug — a marketing platform, your own mail server, a CRM — and we'll show you the SPF, DKIM, and DMARC results with a plain-English explanation of what passed, what failed, and what to fix.
Every @mailtender.io address is a live inbox. Pick a prefix — or use the one we generate for you — and add it as a recipient in whatever system you want to test. When your message arrives, we run it through SPF, DKIM, and DMARC checks and display the results in your inbox.
Your prefix is your credential. Keep it private and the results stay private. Share it with a colleague and they can see the same inbox. There's no sign-in, no account, and no setup.
If you're getting a green check on Auth Ok, you're good to go. If not, click Details on any message to see what's failing, get the records fixed, and keep sending test messages until it's done.
Sender address, subject, authentication results, and routing metadata. Never message bodies or attachments. This metadata is deleted after 21 days, which is about as long as it should take to troubleshoot an email deliverability issue, even if you really don't know what you're doing. See the Privacy Policy for full details.
If you've ever stared at a bounce message wondering why your DKIM key isn't signing, or shipped an email integration only to find it's landing in spam, this is for you. Consultants, developers, and IT admins use MailTender to verify authentication setups and identify what needs to get fixed.
MailTender also includes a free DNS checker for looking up and validating SPF, DKIM, and DMARC records for any domain. It identifies the sending platform from DKIM selectors, evaluates record syntax, and explains what each record means.
A contact form is coming soon.