550: too many invalid recipients
Xfinity refused the whole message because too many of its recipients were invalid, so nobody received it. Clean the recipient list and send it again.
- Comcast
- Provider
- Permanent (5xx)
- Class
- Sources checked
- Author
At a glance
- Code
- 550
- Provider
- Comcast (Xfinity)
- Temporary or permanent
- PermanentRefused for good: the message comes back to the sender, and resending it gets the same answer.
- Who has to act
- The sender. The fix is on the sending side: your domain, your server or your list.
- What the server says
550 Your message could not be delivered due to too many invalid recipients
What it means
When a message is addressed to too many Xfinity recipients that are invalid, Xfinity rejects it outright with this 550, and none of the recipients get it, the valid ones included. Xfinity does not say how many invalid recipients count as too many. The reply is permanent for that message, and the fix Xfinity gives is to check the distribution list and resend. A likely source is an outdated distribution list or a set of addresses gathered without confirmation.
Common causes
- The distribution list contains many old or mistyped Xfinity addresses.
- Addresses were collected without confirmation, or come from a purchased list.
How to fix it
- 01Check the bounce for the addresses that failed, and remove them.
- 02Validate the rest of the distribution list before resending.
- 03Resend the message to the cleaned list, as Xfinity advises.
- 04Remove hard bounces after every send so the list stays clean.
Sources
What this page rests on, checked on 20 Oct 2026. The explanation is ours; the reply text is the server's.
Related codes
- 550Not an Xfinity customer.The address you sent to does not belong to an Xfinity customer. The failure is permanent, and Xfinity asks bulk mailers to treat it as an unsubscribe.
- 550Mailbox unavailable.The receiving server permanently refused the message for this recipient: the mailbox does not exist, cannot be reached, or the server rejected the message by policy.
550 at other providers
- 550 [SC-001]Outlook.com policy block for content or reputation.Outlook.com rejected the mail for policy reasons tied to spam-like content or to the reputation of the sending IP or domain.
- 550 [SC-002]Outlook.com block for namespace mining.Outlook.com blocked the sending IP because it behaved like a namespace miner, checking whether addresses exist without sending mail.
- 550 [SC-003]Outlook.com block for an open proxy or relay.Outlook.com rejected the mail because the sending IP appears to be an open proxy or open relay.
- 550 [SC-004]Outlook.com block after complaints.Outlook.com placed a block on the sending IP because it received complaints about mail coming from it.
- 550 [DY-001]Outlook.com refuses dynamic IP addresses.Outlook.com rejected the mail because the sending IP is dynamic address space, which it generally does not accept mail from.
- 550 [DY-002]Outlook.com block for a likely compromised sender.Outlook.com rejected the mail because the sending server or computer appears to be compromised or infected.
Further reading
All 33 Comcast codesEvery code in the wikiPaste your own bounce