Codepen uses SparkPost as their primary email service provider. They rank #3,749 in the Tranco list of most-popular domains. We've also observed sends via Postmark. Their email authentication setup is good (score 80/100). We've recorded 1 ESP change since first observing this brand.
Authentication signals observed in this brand's emails. SPF, DKIM and DMARC are the standard sender-authentication stack — see the DMARC policy below for whether spoofing is actually blocked or just monitored. One-click unsubscribe meets Google & Yahoo's bulk-sender requirements.
SPF / DKIM / DMARC above reflect the last 2 emails we've observed. DMARC policy is read live from DNS.
DMARC reports sent to fdmarc.net. Policy
p=quarantine means receivers actively block or quarantine spoofed mail.
SPF alignment: all 15 observed emails use a return-path aligned with codepen.io (bounce.codepen.io, pm-bounces.codepen.io). SPF authenticates the visible From — supports DMARC directly.
DKIM alignment: all 15 observed emails sign with a domain aligned with codepen.io (codepen.io). DKIM authenticates the visible From — supports DMARC directly.
TLS: 33% TLS 1.3, 67% TLS 1.2 (across 9 sends).
2 of 2 emails in the last 7 days were delayed beyond 5 minutes (100%) — some sends took over an hour to arrive. Slow sends averaged 1 h 14 min. Healthy senders deliver in under 30 seconds. Consistent delays usually mean greylisting, reputation-based throttling, or receiver-side filter scrutiny — worth investigating sender reputation and authentication setup.
Brands often use multiple ESPs (e.g. one for marketing, another for transactional/notifications).
Postmark 6ESPs we've seen sending email for this brand. Green = confirmed by SPF, sender IP rDNS, or known infra pairing (label shows the source). Grey = observed but not yet confirmed by SPF or PTR.
No additional ESPs authorized in the brand's SPF beyond the confirmed senders above.
Probed: codepen.io, bounce.codepen.io, pm-bounces.codepen.io
Folder distribution across all emails from this brand observed in Gmail inboxes. High inbox % = good deliverability; spam appearances are the headline signal.
| Folder | Count | Share |
|---|---|---|
| inbox | 8 | 72.7% |
| promotions | 3 | 27.3% |
Which ESP's emails are landing where. Sorted by spam % so problem senders surface first. Brands using one ESP for marketing and another for transactional often see very different placement profiles per ESP. Per-ESP folder data only started being captured recently — counts here may be smaller than the total above until backfill catches up.
| ESP | Emails | Placement | Inbox % | Tabs % | Spam % |
|---|---|---|---|---|---|
| Postmark | 3 | 100.0% | 0.0% | 0.0% | |
| SparkPost | 7 | 71.4% | 28.6% | 0.0% |
Monthly observations per ESP. Brands often run multiple ESPs concurrently — marketing on one, transactional on another — so this chart shows usage rather than switches.
IP addresses codepen.io has been observed sending from, and where their mail landed in Gmail.
| IP | Hostname | Obs | Placement | Reputation |
|---|---|---|---|---|
| 192.174.87.53 | mta-174-87-53.smtp-out.sparkpostmail.com |
6 | — | Check → |
| 50.31.156.115 | sc-ord-mta115.mtasv.net |
6 | — | Check → |
| 147.253.211.27 | mta-253-211-27.smtp-out.sparkpostmail.com |
2 | 2 | Check → |
| 192.174.87.79 | mta-174-87-79.smtp-out.sparkpostmail.com |
1 | — | Check → |
| 147.253.215.160 | mta-253-215-160.smtp-out.sparkpostmail.com |
1 | — | Check → |