Mailbox provider · Juno
How to verify a juno.com email address
Juno addresses usually come back inconclusive from a mailbox check. On 13 October 2026 the juno.com mail server mx.dca.untd.com refused our checking server at the greeting stage, citing a Validity Sender Score blocklist listing for the connecting server's IP. A refusal like that says nothing about whether the address exists.
Mailbox checks: Hard to verify. The server refuses connections it does not trust before answering about the mailbox.
Juno at a glance
| Same mailbox system | netzero.net publishes the same MX hosts, mx.dca.untd.com and mx.vgs.untd.com, and sent the identical refusalObserved 13 October 2026 (dig MX) |
|---|---|
| MX hosts | mx.dca.untd.com, mx.vgs.untd.comObserved 13 October 2026 (dig MX) |
| Answer to a made-up address | Connection refused at the greeting: 550 IP in bl.senderscore.com : Access Denied, please see sendersupport.senderscore.netObserved 13 October 2026 (SMTP probe of a made-up recipient, no message sent) |
What Juno's server says about a missing mailbox
Juno's server replied 550 IP in bl.senderscore.com : Access Denied, please see sendersupport.senderscore.net. That refusal happened at the greeting stage, before the checking server could name any recipient, so it is a verdict on the connecting server, not on the address. SimpleVerifier returns these as risky with "Mailbox check unavailable" and never as invalid, because treating a refusal as "mailbox not found" would delete real customers from your list.
Servers screen connections this way to keep spam out: missing reverse DNS, a low sending reputation or a blocklist listing are the usual triggers. The same screen applies to every checking service that connects from a shared or new IP, which is why juno.com results differ between verifiers. SMTP verification false positives explains how much to trust each answer.
Juno and NetZero are both United Online services (untd.com), so one blocklist decision covers both domains.
Cleaning juno.com addresses you can't check
Treat inconclusive juno.com results as unknown, not bad. The checks that don't need the mailbox still work: format, typo domains, duplicates and whether the domain can receive mail. The free list health check runs those in the browser.
For the rest, use the address's history. An address that signed up, bought or replied recently is very likely live. For old or bought data at juno.com, send a small batch first and suppress anything that hard-bounces. If the juno.com share of your list is small, it's often simpler to keep those rows out of a high-risk campaign than to guess.
Live DNS check for juno.com
These are juno.com'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)
2 mail server(s), primary mx.dca.untd.com
SPF — authorised senders
SPF present, neutral (?all) — provides little protection
Common questions
- Can I check if a juno.com address exists without emailing it?
- Usually not from a checking service. On 13 October 2026 Juno's server refused our checking connection at the greeting stage, before any mailbox question, so the result is inconclusive rather than valid or invalid.
- What mail servers does juno.com use?
- On 13 October 2026, juno.com published these MX hosts: mx.dca.untd.com, mx.vgs.untd.com. You can look them up yourself with the free MX lookup tool.
- Should I delete juno.com addresses that come back risky?
- No. For juno.com, 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 Juno 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.