Cal uses Postmark as their primary email service provider. They rank #12,143 in the Tranco list of most-popular domains. We've also observed sends via SendGrid. Their email authentication setup is solid (score 95/100).
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 4 emails we've observed. DMARC policy is read live from DNS.
DMARC reports sent to dmarc-report.com. Policy
p=quarantine means receivers actively block or quarantine spoofed mail.
SPF alignment: all 15 observed emails use a return-path aligned with cal.com (pm-bounces.cal.com, em7290.cal.com). SPF authenticates the visible From — supports DMARC directly.
DKIM alignment: all 10 observed emails sign with a domain aligned with cal.com (cal.com). DKIM authenticates the visible From — supports DMARC directly.
VMC issued by: entrust.
TLS: modern — 100% TLS 1.3 (across 8 sends).
Delivery: fast — 100% of emails in the last 7 days arrive in under 10 seconds (across 2 sends).
Brands often use multiple ESPs (e.g. one for marketing, another for transactional/notifications).
SendGrid 1ESPs 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.
ESPs this brand has authorized in their SPF record. We confirm them with a green ✓ only after seeing recurring use (3+ emails across 2+ days). Until then they stay here — either we haven't observed any email yet, or we've seen a handful but not enough to call them a regular sender for the brand.
Probed: cal.com, pm-bounces.cal.com, em7290.cal.com
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 | 17 | 100.0% |
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 | 14 | 100.0% | 0.0% | 0.0% | |
| SendGrid | 1 | 100.0% | 0.0% | 0.0% |
Daily 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 cal.com has been observed sending from, and where their mail landed in Gmail.
| IP | Hostname | Obs | Placement | Reputation |
|---|---|---|---|---|
| 104.245.209.203 | mta203a-ord.mtasv.net |
6 | — | Check → |
| 104.245.209.231 | mta231b-ord.mtasv.net |
2 | — | Check → |
| 50.31.205.207 | mta207-ab1.mtasv.net |
2 | — | Check → |
| 50.31.205.206 | mta206-ab1.mtasv.net |
2 | 1 | Check → |
| 50.31.46.13 | pnkfnzhd.outbound-mail.sendgrid.net |
1 | — | Check → |
| 104.245.209.201 | mta201a-ord.mtasv.net |
1 | — | Check → |
| 104.245.209.200 | mta200a-ord.mtasv.net |
1 | — | Check → |
| 50.31.205.205 | mta205-ab1.mtasv.net |
1 | — | Check → |
| 104.245.209.237 | mta237b-ord.mtasv.net |
1 | 1 | Check → |