Business mail platform · IONOS
Verifying addresses at IONOS domains
Can you verify addresses at domains behind IONOS?
Depends on the domainIt depends on the company. Domains behind IONOS are probed like any other.
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IONOS answers for the company's own mail rules, so the checker treats every domain on its own: it offers a random address first, and if that is accepted the domain is catch-all and results come back risky ("Accepts all addresses"). Otherwise your address gets a per-mailbox answer. It always checks the syntax, the domain's MX records, disposable domains and role addresses such as info@ first.
Mailbox existsMailbox not foundAccepts all addressesCompany domains whose MX records point at ionos.com are hosted at IONOS. IONOS documents a catch-all option, and where an admin turns it on every address at the domain looks deliverable. Our checker probes each domain on its own: it offers a random address that can't exist first, and a domain that accepts it comes back risky as catch-all; otherwise your address gets a per-mailbox answer.
Live DNS snapshot: ionos.com
Checked 26 October 2026, 07:05 UTCRead from DNS at the time shown and refreshed at most once a day. MX says where mail for ionos.com goes; SPF and DMARC describe mail sent from it, not whether any one address exists.
- 10
mxint01.1and1.com - 10
mxint02.1and1.com
v=spf1 redirect=_spf-corporate.ionos.comp=reject: meets the requirement and enforces it.
v=DMARC1; p=reject; sp=reject; rua=mailto:sdwcwvtj@rua.eu.dmarcmanager.app; ri=86400; aspf=r; adkim=rLook up any other domain with the MX lookup or the email provider lookup.
IONOS at a glance
| Operated by | IONOS SE, Elgendorfer Str. 57, 56410 Montabaur, Germany (German imprint); IONOS Inc. for the US siteSource: IONOS imprint (German) |
|---|---|
| MX hosts | mx00.ionos.com and mx01.ionos.com for IONOS.com customers; mx00.ionos.de and mx01.ionos.de for IONOS Germany customersSource: IONOS help: adjusting MX records |
| Address rule | IONOS Mail Basic and Mail Business support a catch-all: create an address with an asterisk as the name, for example *@example.comSource: IONOS help: catch-all email address |
| Address rule | IONOS says its MX servers are country-specific: .com for IONOS.com, .de for IONOS GermanySource: IONOS help (German): MX-Einträge anpassen |
IONOS domains can be catch-all by one setting
IONOS tells customers to point MX at `mx00.ionos.com` and `mx01.ionos.com`, or the .de pair for German contracts.
IONOS also documents a catch-all address: an address named * that receives mail for names that do not exist. Where that is on, every address at the domain looks deliverable, so a single-address check cannot confirm a person. Where it is off, unknown names are not caught by this feature.
What our checker does behind IONOS
SimpleVerifier doesn't skip or special-case IONOS. For each company domain it offers a random address that can't exist, then your address, and disconnects without sending. If the random address is accepted, the domain is catch-all and its results come back risky with "Accepts all addresses". If it is rejected, your address gets a real answer for that mailbox.
Consumer mailboxes are a separate case; see the Gmail and Yahoo pages. Domains behind IONOS are treated like any company domain.
Cleaning a list full of IONOS domains
Split the list by domain, not by platform. Two companies on IONOS can behave in opposite ways, so a catch-all result at one says nothing about the next. The bulk catch-all checker finds which domains in a list accept everything before you spend time on single addresses.
For catch-all domains, keep addresses with recent replies or sign-ups and send the rest in a small first batch, suppressing anything that hard-bounces. For per-mailbox domains, trust the verdict: invalid addresses will bounce, and valid ones were accepted by the company's own directory. Accept-all vs unknown results covers the difference.
Common questions
- Can you verify addresses at domains behind IONOS?
- It depends on the company. Domains behind IONOS are probed like any other. IONOS answers for the company's own mail rules, so the checker treats every domain on its own: it offers a random address first, and if that is accepted the domain is catch-all and results come back risky ("Accepts all addresses"). Otherwise your address gets a per-mailbox answer. It always checks the syntax, the domain's MX records, disposable domains and role addresses such as info@ first.
- How do I know if a company uses IONOS?
- Look up the domain's MX records. A first MX host ending in ionos.com means mail goes through IONOS. The email provider lookup and MX lookup tools show it for any domain.
- Are domains behind IONOS catch-all?
- Some are and some aren't; it depends on how each company configured IONOS. A verifier can tell by offering a random address that can't exist: if the domain accepts it, the domain is catch-all and single addresses there can't be confirmed.
- What are the IONOS MX hosts?
- IONOS documents mx00.ionos.com and mx01.ionos.com for IONOS.com customers, and mx00.ionos.de and mx01.ionos.de for German customers. Older mx00.1and1.com and mx00.kundenserver.de names are listed as alternatives.
Related tools
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