A1 email checker: does this aon.at or a1.net mailbox exist?
In short: Asks A1's mail server whether an aon.at or a1.net mailbox exists, without sending anything, after syntax, domain, disposable and role checks. Limit: A valid result shows A1 accepted the mailbox today, not that anyone reads it.
To check if an aon.at or a1.net address exists, enter it here. The checker asks A1's mail server about the mailbox at RCPT TO, then disconnects before any message is sent. Both domains rejected a made-up address with 550 5.7.1 … Recipient address rejected: mailbox not found on 8 November 2026, so a missing mailbox comes back invalid.
Price: this tool is free. Checking a whole email list is from $9/mo, and the first 100 checks are free with Google, no card. Check your list free nowSee pricing
Tuned for aon.at, a1.net. Five checks a minute, no account needed. Nothing is sent to the address — we ask its mail server whether the mailbox exists, then disconnect.
Sample result
[email protected] doesn't exist: A1's server rejected it.
- [email protected]
- Reason
- Mailbox not found
- Mailbox check
- SMTP, nothing sent
What this means for you
Invalid means remove it; a real mailbox would come back valid.
- Asks A1's server at RCPT TO
- Catch-all test with a random address first
- Catches typo domains with no mail server
- Flags disposable and role addresses
- A1
- aon.at
- a1.net
By SimpleVerifier Team · Last updated
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How do I check a whole list of A1 and aon.at addresses?
- Export the list as a CSV or copy the email column; A1 and aon.at rows and every other domain can go in together.
- Upload or paste it at /verify. The first 100 email checks are free with a Google sign-in, no card.
- For every list after that, Pro includes unlimited email verification. Fair use: the first 100,000 checks a month at full speed, then slower, never cut off.
How do I check an A1 or aon.at email address?
- Type or paste one address, such as
[email protected]or[email protected]. - Press Check. The tool checks the syntax and domain, asks A1's server about a random address that can't exist, then about yours, and disconnects before anything is sent.
- Read the verdict: valid means A1 accepted the mailbox and rejected the made-up one, invalid means it said the mailbox wasn't found, risky means the check didn't get a clear answer.
- If it comes back risky, check again later: with A1 that is usually a cut-short check, not a bad address.
Example
- You enter
- One address:
[email protected]. - You get
- Valid when A1 accepts the mailbox after rejecting a random address; invalid ("Mailbox not found") when it answers
550 5.7.1 … mailbox not found; risky only when the check gets no clear answer. - Limits
- Five checks a minute per IP address, one address at a time, no account needed.
How do I check if an aon.at or a1.net address exists without emailing it?
Ask A1's mail server instead of the mailbox. On 8 November 2026 both aon.at and a1.net published the same MX host, smx01.a1.net. That day a made-up address on each domain got 550 5.7.1 … Recipient address rejected: mailbox not found at RCPT TO through this checker.
5.7.1 is usually a policy code, but the text says "mailbox not found" and it came at RCPT TO for a recipient that can't exist, so a missing A1 mailbox comes back invalid ("Mailbox not found") and an accepted one valid. This is one check on one day; we have no earlier observation for these domains.
Why do aon.at and a1.net addresses go dead?
A1 mail addresses come with an A1 product. A1's cancellation page warns that services and options included in the product, such as email addresses, are removed after cancelling. Its FAQ on keeping mail after cancelling starts from the same point, that A1 email addresses are deleted, and says forwarding set up beforehand works for 12 months after the cancellation takes effect.
So an aon.at address from a former A1 customer may be gone, or may still forward for up to a year. Re-check Austrian lists before a campaign, for example with the bulk verifier; the GMX email checker covers gmx.at and other GMX domains.
What can this checker confirm at A1?
Each row is something the check runs on an A1 address, and the result you can get from it.
| Check | Can we confirm it? | Result when it fails |
|---|---|---|
| Syntax (the address is written correctly) | Yes | Invalid |
| Domain and mail server (MX) | Yes | Invalid, with a typo suggestion where one fits |
| Disposable or role address | Yes | Invalid (disposable) or risky (role) |
| The mailbox exists | Yes: A1 answers at RCPT TO (550 5.7.1 mailbox not found) | Invalid, "Mailbox not found" |
| A temporary reply or timeout | No answer to read | Risky, worth checking again later |
| Someone reads the inbox | No checker can | Use opens, replies or a small first send |
Our checking server offered a made-up address and disconnected without sending, through this checker on 8 November 2026; earlier checks are dated in the text.
Who uses this tool, and for what?
- Austrian shops and newsletters
- Drop deleted aon.at and a1.net mailboxes before a campaign.
- Support teams
- Catch a mistyped address, or a typo domain like aon.att, before you reply.
- Lead buyers
- Confirm a handful of Austrian ISP contacts before paying for or importing a list.
What can’t this tool tell you?
- A valid result shows A1 accepted the mailbox today, not that anyone reads it.
- A temporary reply or a refused connection comes back risky, not invalid.
- A1 doesn't publish how its servers answer mailbox checks; the handling here is from one check on 8 November 2026, which can change.
- One address at a time, five a minute.
Common questions
- How do I check if an aon.at email address is valid?
- Enter it here. The checker confirms the syntax and mail server, then asks A1's server about the mailbox without sending. It rejected a made-up aon.at address on 8 November 2026, so a missing mailbox comes back invalid.
- Is aon.at email run by A1?
- On 8 November 2026 the aon.at and a1.net domains both used A1's MX host smx01.a1.net, and both gave the same mailbox-not-found reply.
- What happens to my A1 email address if I cancel?
- A1 says email addresses included in the product are removed after cancelling. Forwarding set up beforehand works for 12 months after the cancellation takes effect.
- What does 550 5.7.1 mailbox not found mean from A1?
- A1's server said the mailbox wasn't found. Coming at RCPT TO for an address on its own domain, treat it as a hard bounce and remove the address.
- Is this checker free?
- Yes, five checks a minute with no account. For a whole list, sign in with Google for 100 free email checks, no card, or use a monthly plan.
Sources
That was one address. Most people have a list.
The free checker does five addresses a minute, one at a time — fine for spot-checking, useless for a CSV of 40,000.
- Upload a CSV up to 100,000 rows
- Valid, risky and invalid exported as separate files
- Repeat checks free for 14 days, no new connections
Plans from $9 a month, cancel anytime, no contract. Sign in with Google and your first 100 email checks are free, no card. The free tools stay free either way.