Email Troubleshooter
What’s going wrong?
Why email fails, and how this finds the cause
Most email problems trace back to a handful of causes: missing or broken authentication (SPF, DKIM, DMARC), a poor sending reputation (blocklists, missing reverse DNS), or a receiving setup that senders can’t reach (MX records, the mail server, MTA-STS).
The troubleshooter starts from what you’re seeing, runs only the checks that can explain it, and ranks the causes by how strongly the evidence points at them. Each cause comes with the fix: exact DNS records to paste where possible, otherwise the steps and the tool to dig deeper.
SPF
A TXT record listing the servers allowed to send for your domain.
DKIM
A signature on each message, checked against a public key in DNS.
DMARC
Tells receivers what to do with mail that fails SPF and DKIM alignment, and where to send reports.
MX
The records naming the servers that receive mail for your domain.
How to use this tool
1
Pick the problem
Going to spam, not arriving, bouncing, can’t send, arriving late, or someone sending as you.
2
Enter your domain
Or your email address — only the domain after @ is used.
3
Read the most likely cause
Causes are ranked by evidence, with a confidence level.
4
Apply the fix plan
Copy the records, follow the steps, then run the troubleshooter again to confirm.
Learn more
Guides & explainers related to this tool
Related tools
8 tools
Email Health Checker
Comprehensive email deliverability check including SPF, DKIM, DMARC, and MX records
Email Header Analyzer
Parse and analyze email headers, including SPF, DKIM and DMARC authentication results and routing information
SMTP Test
Test an SMTP server end to end with a timed connection trace covering TLS, login and recipient acceptance, and optionally send a test email
SPF Lookup
Check Sender Policy Framework (SPF) records for email authentication and mail server authorization
DKIM Lookup
Find DomainKeys Identified Mail (DKIM) records for email message signing and verification
DMARC Lookup
Check DMARC policy records for email authentication, reporting, and policy enforcement
IP Blacklist Checker
Check if IP address is blacklisted across multiple DNSBL and spam databases
MX Lookup
Find mail exchange (MX) records for email server configuration and priority
Frequently asked questions
6 Q&A
Usually the MX records are missing or wrong, the mail server isn’t reachable on port 25, a recent MX change hasn’t reached every resolver yet, or an MTA-STS policy in enforce mode doesn’t list your mail server. Mail can also be held in a quarantine or caught by a forwarding rule.
Gmail rejected the message because it failed DMARC: neither SPF nor DKIM passed for a domain aligned with the From address. Fix SPF and turn on DKIM signing — the troubleshooter’s “Bouncing back” check shows which is missing.
Check the port and encryption (587 with STARTTLS or 465 with SSL/TLS — port 25 is usually blocked), use an app password if the account has two-factor sign-in, and in Microsoft 365 make sure Authenticated SMTP is enabled for the mailbox. The troubleshooter confirms your provider’s sending server is reachable.
Publish DMARC with p=quarantine or p=reject and an rua= reporting address, keep SPF and DKIM passing for your real senders, then watch the reports. With p=none, spoofed mail is still delivered.
No. The troubleshooter only reads public DNS records and connects to mail servers to read their greeting and capabilities. It never logs in or sends a message.