Setting up an IONOS email address on a third-party email client raises compatibility questions that other providers have resolved long ago. IONOS does not use OAuth2 on its SMTP servers, which changes the procedure depending on whether you are working on Outlook, Gmail, or Apple Mail. This article compares the exact server settings for each client and identifies the discrepancies that cause most connection errors.
IONOS Server Settings: IMAP and SMTP Comparison Table
Before touching a client, you need to have the correct values. The common issue arises from confusion between the hostnames depending on the geographical area of the account (ionos.fr, ionos.de, ionos.com) and between the two accepted SMTP ports.
| Protocol | Server | Port | Encryption |
|---|---|---|---|
| IMAP (incoming) | imap.ionos.fr | 993 | SSL/TLS |
| SMTP (outgoing) | smtp.ionos.fr | 465 | SSL/TLS |
| SMTP (outgoing, alternative) | smtp.ionos.fr | 587 | STARTTLS |
| POP (incoming, not recommended) | pop.ionos.fr | 995 | SSL/TLS |
The login identifier is always the full IONOS email address, associated with the password set in the customer area. No OAuth window appears: IONOS enforces password authentication on both IMAP and SMTP.
A detailed guide on IONOS IMAP configuration on Geekovision lists the variations of hostnames and the pitfalls related to legacy 1&1 offers.
IONOS SMTP Port: Choosing Between 465 and 587
Both ports work, but not in the same way. The difference lies in the encryption mode and the behavior of certain networks.
Port 465 uses SSL/TLS from the moment the connection is opened. The client establishes an encrypted tunnel before sending any data. This operation is more reliable behind a corporate firewall or a filtered Wi-Fi network because the negotiation does not go through a plaintext phase.
Port 587 starts in plaintext and then switches to encryption via the STARTTLS command. Some networks block or intercept this transition step, causing intermittent sending errors. However, 587 remains the default port in several automatic configuration wizards, which explains its presence in many tutorials.
If you are configuring an IONOS account and sending fails without an explicit error message, testing port 465 with SSL/TLS resolves most blocks.
Outlook and IONOS Email Address: Forcing Manual Configuration
The account addition wizard in Outlook (desktop or new client) first attempts automatic server detection. With IONOS, this detection frequently fails because the provider does not publish an Autodiscover file in the format expected by Microsoft.
Procedure on Classic Outlook (Desktop)
- Open File, then Add Account. Enter the IONOS address, click on Advanced Options, check “Let me set up my account manually”
- Select IMAP as the account type. Enter imap.ionos.fr on port 993 (SSL/TLS) for incoming and smtp.ionos.fr on port 465 (SSL/TLS) for outgoing
- Ensure that SMTP authentication is enabled with the same credentials as the incoming server. Without this option, sending will be rejected
On the new Outlook client (unified web version), the procedure is similar, but the interface sometimes suggests connecting via a Microsoft account. You should ignore this suggestion and manually enter the IONOS server settings.
Common Error on Outlook
Outlook sometimes activates the POP protocol by default instead of IMAP. A POP account downloads messages and deletes them from the server, which desynchronizes the inbox across multiple devices. Check the protocol type in the account settings if your emails disappear from one device after being read on another.
Gmail: Receiving and Sending with an IONOS Account
Gmail allows you to add an external account via the “Check mail from other accounts” feature in the settings. Receiving goes through POP in the Gmail web interface, which is a technical limitation.
For sending, Gmail offers to send messages “as” the IONOS address. This step requires entering smtp.ionos.fr, port 465, and SSL encryption. Gmail then requests a verification code sent to the IONOS address to validate the association.
The main constraint on Gmail remains the absence of IMAP for import. Messages retrieved via POP arrive in the Gmail inbox without bidirectional synchronization. An email read in Gmail will not be marked as read in the IONOS webmail. For complete folder synchronization, a heavy client (Outlook, Thunderbird, Apple Mail) connected via IMAP is preferable.
Apple Mail and IONOS Account on macOS and iOS
Apple Mail detects IONOS servers better than most clients, but a manual check avoids unpleasant surprises. On macOS, the path goes through System Settings, then Internet Accounts, then Add Another Account, then Mail Account.
The point of caution concerns the explicit activation of SSL encryption in the server settings. Apple Mail may accept an unencrypted connection without a visible warning, exposing credentials in plaintext over the network. After creating the account, open the advanced settings of the account in Mail and check that the SSL box is checked for the incoming server (port 993) and the outgoing server (port 465).
On iOS, the procedure in Settings, then Mail, then Accounts follows the same logic. SMTP authentication must be manually enabled in the outgoing server settings, as iOS sometimes disables it by default for accounts added in “Other” mode.
The hostname remains the determining factor across the three clients. An account provisioned on the German platform of IONOS will use imap.ionos.de and smtp.ionos.de instead of the .fr variants. If connection fails with standard settings, checking the account’s area in the IONOS customer area helps clarify any ambiguity.