Slack uses Bloomreach for marketing email and Amazon SES for transactional/notifications. They rank #326 in the Tranco list of most-popular domains. Email goes out from 2 different subdomains. Their email authentication setup is solid (score 85/100).
Amazon SESNon-ESP tools detected in this brand's emails. Independent of who sends — a brand can use any combination.
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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 10 emails we've observed. DMARC policy is read live from DNS.
DMARC reports sent to Red Sift OnDMARC. Policy
p=reject means receivers actively block or quarantine spoofed mail.
SPF alignment: 99% of observed emails use an aligned return-path (mail.slack.com, bounce.slack-mail.com, bounce.us-west-2.slack-mail.com); the rest use third-party paths (gmail.com) where DMARC has to rely on DKIM alignment.
DKIM alignment: all 405 observed emails sign with a domain aligned with slack.com (slack.com, slack-mail.com). DKIM authenticates the visible From — supports DMARC directly.
TLS: modern — 100% TLS 1.3 (across 196 sends).
Delivery: fast — 80% of emails in the last 7 days arrive in under 10 seconds (across 87 sends).
Brands often use multiple ESPs (e.g. one for marketing, another for transactional/notifications).
None — only the primary ESP(s) shown aboveESPs 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: slack.com, mail.slack.com, bounce.us-west-2.slack-mail.com, bounce.slack-mail.com, gmail.com, slack-mail.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 | 464 | 99.6% |
| spam | 2 | 0.4% |
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 % |
|---|---|---|---|---|---|
| Amazon SES | 428 | 99.5% | 0.0% | 0.5% | |
| Bloomreach | 1 | 100.0% | 0.0% | 0.0% | |
| Sarbacane | 1 | 100.0% | 0.0% | 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 slack.com has been observed sending from, and where their mail landed in Gmail.
| IP | Hostname | Obs | Placement | Reputation |
|---|---|---|---|---|
| 76.223.142.184 | c142-184.smtp-out.amazonses.com |
27 | 2 | Check → |
| 54.240.37.230 | a37-230.smtp-out.amazonses.com |
25 | 7 | Check → |
| 76.223.142.190 | c142-190.smtp-out.amazonses.com |
25 | 4 | Check → |
| 76.223.146.39 | c146-39.smtp-out.us-west-2.amazonses.com |
20 | 3 | Check → |
| 76.223.146.35 | c146-35.smtp-out.us-west-2.amazonses.com |
20 | 2 | Check → |
| 54.240.37.231 | a37-231.smtp-out.amazonses.com |
19 | 4 | Check → |
| 76.223.146.32 | c146-32.smtp-out.us-west-2.amazonses.com |
19 | 1 | Check → |
| 76.223.142.188 | c142-188.smtp-out.amazonses.com |
18 | 7 | Check → |
| 76.223.146.31 | c146-31.smtp-out.us-west-2.amazonses.com |
17 | 2 | Check → |
| 76.223.146.28 | c146-28.smtp-out.us-west-2.amazonses.com |
17 | 7 | Check → |
| 23.249.223.6 | d223-6.smtp-out.us-west-2.amazonses.com |
16 | 3 | Check → |
| 76.223.142.186 | c142-186.smtp-out.amazonses.com |
15 | 3 | Check → |
| 76.223.142.191 | c142-191.smtp-out.amazonses.com |
14 | 3 | Check → |
| 76.223.146.36 | c146-36.smtp-out.us-west-2.amazonses.com |
14 | 6 | Check → |
| 76.223.146.34 | c146-34.smtp-out.us-west-2.amazonses.com |
13 | 4 | Check → |
| 76.223.142.183 | c142-183.smtp-out.amazonses.com |
13 | 1 | Check → |
| 76.223.142.187 | c142-187.smtp-out.amazonses.com |
13 | 1 | Check → |
| 76.223.146.38 | c146-38.smtp-out.us-west-2.amazonses.com |
13 | 1 | Check → |
| 23.249.223.5 | d223-5.smtp-out.us-west-2.amazonses.com |
13 | 3 | Check → |
| 76.223.142.189 | c142-189.smtp-out.amazonses.com |
12 | 2 | Check → |
| 76.223.142.185 | c142-185.smtp-out.amazonses.com |
12 | 3 | Check → |
| 76.223.146.27 | c146-27.smtp-out.us-west-2.amazonses.com |
11 | 3 | Check → |
| 76.223.142.192 | c142-192.smtp-out.amazonses.com |
11 | 4 | Check → |
| 76.223.146.30 | c146-30.smtp-out.us-west-2.amazonses.com |
11 | 4 | Check → |
| 76.223.146.33 | c146-33.smtp-out.us-west-2.amazonses.com |
10 | — | Check → |
| Domain | ESPs detected | Delivery (7d) |
|---|---|---|
slack.com | Amazon SES 475 | |
slack-mail.com | Amazon SES 32 Bloomreach 1 |