diff --git a/backend/README.md b/backend/README.md
index 72c6db051..6621118c1 100644
--- a/backend/README.md
+++ b/backend/README.md
@@ -55,7 +55,6 @@ These are the environment variables used to configure the HTTP server. To pass t
 | `RCH_HTTP_HOST`                     | No                          | The host name to bind the HTTP server to.                                                                                                                                                                                                  | `127.0.0.1` |
 | `PORT`                              | No                          | The port to bind the HTTP server to, often populated by the cloud provider.                                                                                                                                                                | `8080`      |
 | `RCH_HOTMAIL_USE_HEADLESS`          | No                          | Set to a running WebDriver process endpoint (e.g. `http://localhost:4444`) to use a headless navigator to Hotmail's password recovery page to check Hotmail/Outlook addresses. We recommend `chromedriver` as it allows parallel requests. | not defined |
-| `RCH_SMTP_TIMEOUT`                  | No                          | The default timeout of each SMTP connection, in seconds. Can be overwritten in each request using the `smtp_timeout` field.                                                                                                                | 10s         |
 | `RCH_SENTRY_DSN`                    | No                          | If set, bug reports will be sent to this [Sentry](https://sentry.io) DSN.                                                                                                                                                                  | not defined |
 | `RCH_HEADER_SECRET`                 | No                          | If set, then all HTTP requests must have the `x-reacher-secret` header set to this value. This is used to protect the backend against public unwanted HTTP requests.                                                                       | undefined   |
 | `RCH_DATABASE_MAX_CONNECTIONS`      | No                          | (Bulk) Connections created for the database pool                                                                                                                                                                                           | 5           |
diff --git a/backend/src/check.rs b/backend/src/check.rs
index aace8f1e9..a3de306f7 100644
--- a/backend/src/check.rs
+++ b/backend/src/check.rs
@@ -26,6 +26,31 @@ use super::sentry_util;
 /// Same as `check-if-email-exists`'s check email, but adds some additional
 /// inputs and error handling.
 pub async fn check_email(input: CheckEmailInput) -> CheckEmailOutput {
+	let hotmail_use_headless = env::var("RCH_HOTMAIL_USE_HEADLESS").ok();
+	let skipped_domains = vec![
+		// on @bluewin.ch
+		// - mx-v02.bluewin.ch.
+		".bluewin.ch.".into(),
+		// on @bluewin.ch
+		// - mxbw-bluewin-ch.hdb-cs04.ellb.ch.
+		"bluewin-ch.".into(),
+		// on @gmx.de, @gmx.ch, @gmx.net
+		".gmx.net.".into(),
+		// on @icloud.com
+		".mail.icloud.com.".into(),
+		// on @web.de
+		".web.de.".into(),
+		".zoho.com.".into(),
+	];
+
+	let input = CheckEmailInput {
+		// If we want to override core check-if-email-exists's default values
+		// for CheckEmailInput for the backend, we do it here.
+		hotmail_use_headless,
+		skipped_domains,
+		..input
+	};
+
 	let res = ciee_check_email(&input).await;
 
 	sentry_util::log_unknown_errors(&res);
diff --git a/core/src/smtp/mod.rs b/core/src/smtp/mod.rs
index 0b56d4c4e..6dc2518f5 100644
--- a/core/src/smtp/mod.rs
+++ b/core/src/smtp/mod.rs
@@ -34,7 +34,7 @@ pub use error::*;
 
 use self::{
 	gmail::is_gmail,
-	outlook::{is_hotmail, is_outlook},
+	outlook::{is_microsoft365, is_outlook},
 	yahoo::is_yahoo,
 };
 
@@ -84,7 +84,7 @@ pub async fn check_smtp(
 			.await
 			.map_err(|err| err.into());
 	}
-	if input.microsoft365_use_api && is_outlook(&host_lowercase) {
+	if input.microsoft365_use_api && is_microsoft365(&host_lowercase) {
 		match outlook::microsoft365::check_microsoft365_api(to_email, input).await {
 			Ok(Some(smtp_details)) => return Ok(smtp_details),
 			// Continue in the event of an error/ambiguous result.
@@ -101,10 +101,7 @@ pub async fn check_smtp(
 	}
 	#[cfg(feature = "headless")]
 	if let Some(webdriver) = &input.hotmail_use_headless {
-		// The password recovery page do not always work with Microsoft 365
-		// addresses. So we only test with @hotmail and @outlook addresses.
-		// ref: https://github.com/reacherhq/check-if-email-exists/issues/1185
-		if is_hotmail(&host_lowercase) {
+		if is_outlook(&host_lowercase) {
 			return outlook::hotmail::check_password_recovery(to_email, webdriver)
 				.await
 				.map_err(|err| err.into());
@@ -144,7 +141,8 @@ mod tests {
 
 		let to_email = EmailAddress::from_str("foo@icloud.com").unwrap();
 		let host = Name::from_str("mx01.mail.icloud.com.").unwrap();
-		let input = CheckEmailInput::default();
+		let mut input = CheckEmailInput::default();
+		input.set_skipped_domains(vec![".mail.icloud.com.".into()]);
 
 		let res = runtime.block_on(check_smtp(&to_email, &host, 25, "icloud.com", &input));
 		match res {
diff --git a/core/src/smtp/outlook/mod.rs b/core/src/smtp/outlook/mod.rs
index 9bcb209f5..6a881b019 100644
--- a/core/src/smtp/outlook/mod.rs
+++ b/core/src/smtp/outlook/mod.rs
@@ -28,3 +28,8 @@ pub fn is_hotmail(host: &str) -> bool {
 	host.to_lowercase()
 		.ends_with(".olc.protection.outlook.com.")
 }
+
+/// Check if an address is a Microsoft365 email address.
+pub fn is_microsoft365(host: &str) -> bool {
+	is_outlook(host) && !is_hotmail(host)
+}
diff --git a/core/src/util/input_output.rs b/core/src/util/input_output.rs
index 71b883d7d..06b7ef42a 100644
--- a/core/src/util/input_output.rs
+++ b/core/src/util/input_output.rs
@@ -176,21 +176,7 @@ impl Default for CheckEmailInput {
 			check_gravatar: false,
 			haveibeenpwned_api_key: None,
 			retries: 2,
-			skipped_domains: vec![
-				// on @bluewin.ch
-				// - mx-v02.bluewin.ch.
-				".bluewin.ch.".into(),
-				// on @bluewin.ch
-				// - mxbw-bluewin-ch.hdb-cs04.ellb.ch.
-				"bluewin-ch.".into(),
-				// on @gmx.de, @gmx.ch, @gmx.net
-				".gmx.net.".into(),
-				// on @icloud.com
-				".mail.icloud.com.".into(),
-				// on @web.de
-				".web.de.".into(),
-				".zoho.com.".into(),
-			],
+			skipped_domains: vec![],
 		}
 	}
 }