IMAP settings · comcast.net
Comcast Xfinity IMAP settings
Comcast blocks mail clients outright until you allow them yourself. The setting is a single checkbox buried in Xfinity Email security, and while it is off, every client fails with what looks like a password problem — the password is fine, the account simply refuses anything that is not the web interface.
IMAP connection
- Server
- imap.comcast.net
- Port
- 993
- Encryption
- SSL/TLS
- Username
- full address
- Password
- the mailbox password
Sending, SMTP
- Server
- smtp.comcast.net
- Port
- 587
- Encryption
- STARTTLS
Checked against the service's own autoconfiguration file on 2026-09-15 — the same source Thunderbird reads when it fills the settings in for you. Source: autoconfig.thunderbird.net, www.xfinity.com
What breaks here.
- Third-party access is off by default. Turn it on at connect.xfinity.com → the gear icon → Email Settings → Security → the box under Third Party Access Security.
- Until that box is ticked no client connects, no matter how right the host, port and password are. The error looks like bad credentials, which is why people spend an evening re-typing their password.
- The username is the full address, including @comcast.net.
- Outgoing mail goes through smtp.comcast.net on port 587 with STARTTLS; the encrypted IMAP port is 993.
Questions
The short answers
Where is the third-party access setting?
Sign in to Xfinity Email at connect.xfinity.com, open the gear icon → Email Settings → Security, and tick the box under Third Party Access Security. It takes effect right away.
Which ports does Comcast use?
IMAP 993 with SSL/TLS (or 143 with STARTTLS), SMTP 587 with STARTTLS or 465 with SSL.
Do I need an app password?
No. Comcast takes the account password over IMAP once third-party access is allowed — the checkbox is the gate here, not a separate password.
Can I move a comcast.net mailbox to Gmail or Microsoft 365?
Yes. Allow third-party access, use imap.comcast.net as the source and the new mailbox as the destination. Nothing is deleted at Comcast: the default mode only copies.
Find out how big your mailbox is. It costs nothing.
Connect two servers, look at the size and decide. Or take the client and keep everything on your side.
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