Domain Intelligence
Last Updated:
Slack.com
Safe to Send
Slack.com is operated by Salesforce Inc.. The domain runs 5 mail exchanges and SMTP is responsive, with 2 of 3 authentication standards in place.
Safe to Send
RISK
17
/100
Low
Verify Mailbox
Verify @slack.com emails
Live SMTP handshake against slack.com mail servers. No email is sent. 10 free per day, no signup.
Trusted by 400,000+ senders
4.9/5
From 8,500+ verified reviews
Reached out to support during our API integration last month. Response in under 15 minutes, the rep was so sharp and helpful that by the end of the thread it honestly felt like I was flirting with him. Amazing support team. A+++. Nathan Orozco · Lead Engineer · via X
SOC 2 Type II
GDPR
CCPA
99.7% Accuracy
Disposable
No
Persistent addresses, not throwaway
SMTP Live
Yes
Mail server responds to SMTP handshake
MX Records
5
Mail exchangers
Mail Exchange (MX) Records for slack.com Mail Exchange records. They tell other mail servers which hosts are responsible for receiving email at this domain, in priority order. Lower priority numbers are tried first.
#1
aspmx.l.google.com 192.178.155.26
Reachable
#5
alt1.aspmx.l.google.com 108.177.123.27
Reachable
#5
alt2.aspmx.l.google.com 172.253.116.27
Reachable
#10
aspmx2.googlemail.com 108.177.123.26
Reachable
#10
aspmx3.googlemail.com 172.253.116.27
Reachable
SMTP Handshake
Simple Mail Transfer Protocol. We open a live SMTP connection to the primary MX and read the greeting banner. A response confirms the mail server is alive and accepting connections.
Responsive
BANNER220 mx.google.com ESMTP af79cd13be357-910bda441b9si898965485a.272 - gsmtp
Primary mail server accepted SMTP connection and returned a banner during the live audit.
slack.com Email Authentication SPF · DKIM · DMARC
SPF
Sender Policy Framework. A DNS record listing which servers are allowed to send mail for this domain. Receivers reject or flag mail from unauthorized servers.
Pass
TXTv=spf1 include:_spf.qualtrics.com include:mail.zendesk.com include:_spfextra.slack.com -all
Authorized senders are defined and pass SPF policy.
DKIM
DomainKeys Identified Mail. The sending server cryptographically signs outbound mail with a private key, and receivers verify the signature using a public key in DNS.
Missing
No DKIM signature detected on common selectors for slack.com.
No DKIM signature was detected. Receivers cannot verify the integrity of outbound mail.
DMARC
Domain-based Message Authentication, Reporting & Conformance. Tells receivers what to do when SPF or DKIM checks fail: none, quarantine, or reject.
Reject
TXTv=DMARC1;p=reject;fo=1:d:s;pct=100;rua=mailto:dmarc_agg@vali.email,mailto:0e5a5c34@inbox.ondmarc.com;ruf=mailto:0e5a5c34@inbox.ondmarc.com
Strict policy. Receivers are instructed to reject any mail that fails SPF or DKIM. The strongest available setting.
slack.com Domain Registration WHOIS · Nameservers · Registrar
RegistrarMarkMonitor, Inc.
IANA ID292
RegisteredOctober 21, 1992
Last UpdatedSeptember 18, 2025
ExpiresOctober 19, 2027
Age33 years
TLD.com
Authoritative Nameservers (4)
- ns-1901.awsdns-45.co.uk
- ns-166.awsdns-20.com
- ns-1493.awsdns-58.org
- ns-606.awsdns-11.net
Registrant
Slack Hostmaster
Slack Technologies, Inc.
hostmaster@slack-corp.com·San Francisco, CA, UNITED STATES·14158058989
Technical Contact
Slack Hostmaster
hostmaster@slack-corp.com·UNITED STATES·14158058989
About this Domain
About slack.com
Slack (slack.com) is a business communication platform owned by Salesforce, headquartered in San Francisco, California. Slack provides channel-based messaging, file sharing, and workflow automation used by millions of daily active users across organizations worldwide. The platform has become the standard for workplace instant messaging and team collaboration.
Slack implements enterprise email authentication on the slack.com domain with SPF, DKIM, and DMARC enforcement. As a ubiquitous workplace tool, Slack faces constant phishing threats from campaigns impersonating workspace notifications, message alerts, and integration requests targeting business professionals.
Email verification against slack.com returns definitive responses for valid and invalid mailboxes. The domain does not operate as catch-all. Slack's mail infrastructure implements rate limiting on inbound SMTP connections consistent with enterprise software companies.
For partners communicating with Slack employees, proper sender authentication is important. Slack's corporate email filters enforce SPF, DKIM, and DMARC validation. Maintaining authentication compliance ensures reliable delivery to slack.com addresses.
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More Email Verification Tools
Free single-address checks, bulk uploads, and APIs for plugging email verification into your own product.
Common Questions About slack.com
Is slack.com a disposable or temporary email provider?
No. slack.com is not a disposable email provider. It is classified as Corporate Email operated by Salesforce Inc. and addresses on slack.com are persistent rather than throwaway. Mail sent to a valid slack.com mailbox reaches a real recipient.
How do I verify if a slack.com email address is valid?
The fastest way to verify a slack.com email address is to use our free email checker. Enter any @slack.com mailbox at the top of this page and our system performs a real-time SMTP handshake against slack.com's mail servers, confirming whether the mailbox exists, is reachable, and is safe to send to. No email is ever delivered during the check.
Can I check if a slack.com email exists without sending a message?
Yes. Our real-time email verification API connects directly to slack.com's mail server, opens an SMTP session, and queries the mailbox using the RCPT TO command without ever transmitting an actual email. The server's response confirms whether the slack.com mailbox is valid, full, or non-existent. The recipient never receives anything and never sees the check.
What are the MX records for slack.com?
slack.com currently publishes 5 mail exchange (MX) records. The primary MX is aspmx.l.google.com, which is the first server contacted when other mail systems try to deliver email to a slack.com address. The full list with priorities and IP addresses is in the MX Records panel above. MX records tell sending servers where to route email for slack.com.
Does slack.com use SPF, DKIM, and DMARC email authentication?
slack.com has 2 of the 3 standard email authentication records in place: SPF, and DMARC (policy: reject). Adding the missing layer(s) would tighten anti-spoofing protection and improve deliverability for legitimate slack.com mail.
Why do emails to slack.com bounce or get blocked?
Bounces from slack.com usually fall into three buckets: the mailbox doesn't exist (5xx user unknown), the inbox is full, or your sending domain isn't authenticated to slack.com's satisfaction. The fastest fix is to run each address through a free email verifier before you send, and to make sure your own SPF, DKIM, and DMARC are configured correctly so slack.com's receivers trust you.
How can I verify a large list of slack.com email addresses?
Our bulk email verifier accepts CSV or TXT uploads with thousands or millions of slack.com addresses (or any mix of domains). Every address goes through 30+ checks including SMTP existence, slack.com catch-all detection, role-account detection, and disposable-domain matching. Results typically come back within minutes and previously-failed addresses on your blacklist are reprocessed for free. For continuous high-volume needs, see our unlimited email verification API.
Is it safe to accept signups from slack.com email addresses?
Yes, with normal hygiene. slack.com is a legitimate email service and signups from @slack.com behave like any other real user. Pipe each address through a real-time email verifier API at the moment of signup to catch typos and dead mailboxes, but there is no need to block slack.com by default.
What email format does slack.com use for usernames?
Most slack.com mailboxes follow common patterns like first.last@slack.com, firstinitiallast@slack.com, or first@slack.com, but the actual local-part rules depend on Salesforce Inc.. The only reliable way to confirm whether a specific @slack.com address exists is to run it through a free email verification tool. Guessing patterns will produce a high bounce rate and damage your sender reputation.
How is the slack.com risk score calculated?
The 0-to-100 risk score for slack.com combines disposable-domain classification, mail-server reachability, MX record presence and depth, SPF / DKIM / DMARC enforcement, DMARC policy strength, SMTP banner response, and domain age. Lower scores mean safer to send to. Disposable domains are pinned at the high end of the scale. The slack.com score is recomputed on every audit so it always reflects the live state of the domain.
Is slack.com a valid email domain?
Yes, slack.com is the official corporate email domain for Salesforce Inc.. It is used for business communications and is not available for public registration.
Is slack.com a disposable or temporary email provider?
No, slack.com is a corporate email domain belonging to Salesforce Inc., used exclusively by employees and authorized personnel.
What mail server does slack.com use?
slack.com uses enterprise-grade mail infrastructure. Check the MX records section above for specific mail server details.
Can I send marketing emails to slack.com addresses?
B2B marketing to slack.com addresses requires proper consent and compliance with anti-spam laws. Corporate domains may use catch-all configurations, so verify addresses before sending.
How do I verify an email address at slack.com?
Corporate domains like slack.com may use catch-all configurations. Use BulkEmailChecker advanced verification to detect catch-all behavior and validate individual addresses.