Comcast Xfinity SMTP settings: smtp.comcast.net, port 587
Xfinity/Comcast outgoing server: smtp.comcast.net, port 587 STARTTLS or 465 SSL, full comcast.net address and password; third-party access must be enabled in Xfinity settings. Port 25 is blocked on Comcast connections.
Comcast / Xfinity outgoing mail server:
smtp.comcast.net, port <code>587</code> (STARTTLS) or <code>465</code> (SSL/TLS), username = your full address, password = your Xfinity password.
Comcast / Xfinity SMTP settings at a glance
| Outgoing (SMTP) host | smtp.comcast.net |
|---|---|
| Ports & encryption |
587 — STARTTLS <em>(recommended)</em>465 — SSL/TLS |
| Username | your full address, e.g. you@comcast.net |
| Password | your Xfinity password (after enabling third-party client access) |
| Authentication | Xfinity Email → Settings → Security → "Third Party Access Security" must be allowed, or every client gets an authentication error. |
How to set up Comcast / Xfinity SMTP
- Xfinity Email settings → Security → allow third-party access.
- App settings: host smtp.comcast.net, port 587 STARTTLS, username = full address, password = Xfinity password.
Sending limits
- Comcast rate-limits residential accounts (about 1,000 recipients per day) and blocks outbound port 25 on residential connections.
Things that catch people out
- If you run your own mail server at home on Comcast, outbound port 25 is blocked: relay through smtp.comcast.net or a relay service on 587.
Common Comcast / Xfinity SMTP errors
| Server reply | Meaning | Fix |
|---|---|---|
535 5.7.0 Authentication failed | Third-party access disabled. | Enable it in Xfinity security settings. |
More codes: 535 authentication failed, 550 relay denied, 554 rejected as spam, connection timed out — or all SMTP error codes.
When Comcast / Xfinity is not enough for your app
When a provider caps you or blocks a port, point the same app at QueenSMTP instead: host smtp.queensmtp.com, port 587 (STARTTLS) or 465 (SSL), your SMTP username and password from the dashboard. $5/year plus $0.10 per 1,000 emails, 100 free a day to test.
Get SMTP credentials — free to test Test Comcast / Xfinity nowRelated settings
Comcast / Xfinity SMTP — questions
smtp.comcast.net on port 587 (STARTTLS) or 465 (SSL), with your full comcast.net address, after allowing third-party access.
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