Error 5.7.26 is a Gmail rejection that means: this message did not pass authentication. Since Google’s 2024 sender requirements, any email sent in bulk to Gmail must align on SPF and DKIM and have a published DMARC record. Without all three, Gmail returns 5.7.26 and the message never reaches the inbox.
What Gmail says “This message does not have authentication information or fails to pass authentication checks.” The fix is always on the sending domain’s DNS, not on Mailpro.
Checklist to fix 5.7.26
| Step | What to check |
|---|---|
| SPF | A TXT record covering Mailpro’s sending IPs — see configure SPF. |
| DKIM | A CNAME (or TXT) record signing your domain — see configure DKIM. |
| DMARC | At minimum a p=none record — see configure DMARC. |
| From domain | Send from your own domain, not a free Gmail/Yahoo address. |
How alignment works
SPF and DKIM must each pass and the domain they validate must match the visible From address. That match is called alignment. Read the basics on SPF, DKIM and DMARC.
Common cause You added Mailpro’s SPF include but kept sending from a generic Gmail address. SPF can’t align on a domain you don’t own.
Authenticate your sending domain
Open the email authentication hub and walk through DNS and SPF configuration — once SPF, DKIM and DMARC are green, the 5.7.26 bounce stops.