Mailbox provider · Shaw
How to check if a shaw.ca email address exists
Shaw addresses can't be confirmed with a mailbox check. On 13 October 2026 the shaw.ca mail server shw-central.mx.a.cloudfilter.net accepted a made-up recipient at RCPT TO with 250 2.1.5 <…@shaw.ca> recipient ok, so real and fake addresses get the same answer. Expect shaw.ca results to come back risky (accept-all), not valid or invalid.
Mailbox checks: Not verifiable. The server accepts any recipient, real or not.
Shaw at a glance
| MX hosts | shw-central.mx.a.cloudfilter.netObserved 13 October 2026 (dig MX) |
|---|---|
| Answer to a made-up address | 250 2.1.5 <…@shaw.ca> recipient ok, returned at RCPT TOObserved 13 October 2026 (SMTP probe of a made-up recipient, no message sent) |
What Shaw's server says about a missing mailbox
Shaw answered our made-up shaw.ca address with 250 2.1.5 <…@shaw.ca> recipient ok at RCPT TO, the step where a verifier names the recipient. When a server says yes to an address that cannot exist, its yes for your real address carries no information. SimpleVerifier tests a random address first for exactly this reason and returns shaw.ca results as risky with the reason "Accepts all addresses".
Accepting at RCPT TO doesn't mean every message is delivered. Providers that do this usually decide later, after the message is sent, and a missing mailbox then produces a bounce rather than an up-front rejection. That is why accept-all results belong in their own segment: accept-all vs unknown results covers how to treat them.
Shaw's mail is filtered by Cloudmark's cloudfilter.net gateway, which accepted the made-up address without checking it against real mailboxes.
Cleaning shaw.ca addresses when the server says yes to everything
Don't delete shaw.ca addresses just because they came back risky; most will be real. Remove what can be proven bad without the mailbox check: syntax errors, typo domains, duplicates and disposable addresses, which the free list health check finds in the browser.
Then send to the shaw.ca segment in a small first batch and watch the bounces. Addresses that bounce as unknown users are gone and should be suppressed; the rest have proved themselves. Engagement history is the other strong signal: an address that opened or replied recently is live whatever the check says. Should you send to catch-all emails? walks through the same approach.
Live DNS check for shaw.ca
These are shaw.ca's own sending records, refreshed daily. They describe mail sent from the domain, not whether a given address at it exists.
3 of 5 checks passed
60%Blocklist status
Not listed on SURBL, SpamCop
DKIM — message signing
No DKIM found on common selectors — it may use a custom one
DMARC — spoofing policy
DMARC present but p=none, so nothing is enforced
Mail servers (MX)
1 mail server(s), primary shw-central.mx.a.cloudfilter.net
SPF — authorised senders
SPF present, soft fail (~all)
Common questions
- Can I check if a shaw.ca address exists without emailing it?
- Not reliably. On 13 October 2026 Shaw's server accepted a made-up shaw.ca address at the RCPT TO step, so a mailbox check gets the same yes for real and fake addresses. Verifiers return shaw.ca addresses as risky (accept-all).
- What mail servers does shaw.ca use?
- On 13 October 2026, shaw.ca published these MX hosts: shw-central.mx.a.cloudfilter.net. You can look them up yourself with the free MX lookup tool.
- Should I delete shaw.ca addresses that come back risky?
- No. For shaw.ca, risky reflects how the server treats checks, not the address. Remove the ones that fail format, typo-domain and duplicate checks, then send to the rest in a small batch and suppress whatever hard-bounces.
Check a Shaw address
The free checker runs the mailbox check on one address and shows the server's reason, so you can see which of the cases above applies.