diff --git a/src/api/admin.rs b/src/api/admin.rs
index 46e39502..3fe4f947 100644
--- a/src/api/admin.rs
+++ b/src/api/admin.rs
@@ -269,7 +269,7 @@ fn invite_user(data: Json<InviteData>, _token: AdminToken, conn: DbConn) -> Json
         if CONFIG.mail_enabled() {
             mail::send_invite(&user.email, &user.uuid, None, None, &CONFIG.invitation_org_name(), None)?;
         } else {
-            let invitation = Invitation::new(data.email);
+            let invitation = Invitation::new(user.email.clone());
             invitation.save(&conn)?;
         }
 
diff --git a/src/api/core/accounts.rs b/src/api/core/accounts.rs
index a38a496b..ee97e82f 100644
--- a/src/api/core/accounts.rs
+++ b/src/api/core/accounts.rs
@@ -62,11 +62,12 @@ struct KeysData {
 #[post("/accounts/register", data = "<data>")]
 fn register(data: JsonUpcase<RegisterData>, conn: DbConn) -> EmptyResult {
     let data: RegisterData = data.into_inner().data;
+    let email = data.Email.to_lowercase();
 
-    let mut user = match User::find_by_mail(&data.Email, &conn) {
+    let mut user = match User::find_by_mail(&email, &conn) {
         Some(user) => {
             if !user.password_hash.is_empty() {
-                if CONFIG.is_signup_allowed(&data.Email) {
+                if CONFIG.is_signup_allowed(&email) {
                     err!("User already exists")
                 } else {
                     err!("Registration not allowed or user already exists")
@@ -75,19 +76,19 @@ fn register(data: JsonUpcase<RegisterData>, conn: DbConn) -> EmptyResult {
 
             if let Some(token) = data.Token {
                 let claims = decode_invite(&token)?;
-                if claims.email == data.Email {
+                if claims.email == email {
                     user
                 } else {
                     err!("Registration email does not match invite email")
                 }
-            } else if Invitation::take(&data.Email, &conn) {
+            } else if Invitation::take(&email, &conn) {
                 for mut user_org in UserOrganization::find_invited_by_user(&user.uuid, &conn).iter_mut() {
                     user_org.status = UserOrgStatus::Accepted as i32;
                     user_org.save(&conn)?;
                 }
 
                 user
-            } else if CONFIG.is_signup_allowed(&data.Email) {
+            } else if CONFIG.is_signup_allowed(&email) {
                 err!("Account with this email already exists")
             } else {
                 err!("Registration not allowed or user already exists")
@@ -97,8 +98,8 @@ fn register(data: JsonUpcase<RegisterData>, conn: DbConn) -> EmptyResult {
             // Order is important here; the invitation check must come first
             // because the vaultwarden admin can invite anyone, regardless
             // of other signup restrictions.
-            if Invitation::take(&data.Email, &conn) || CONFIG.is_signup_allowed(&data.Email) {
-                User::new(data.Email.clone())
+            if Invitation::take(&email, &conn) || CONFIG.is_signup_allowed(&email) {
+                User::new(email.clone())
             } else {
                 err!("Registration not allowed or user already exists")
             }
@@ -106,7 +107,7 @@ fn register(data: JsonUpcase<RegisterData>, conn: DbConn) -> EmptyResult {
     };
 
     // Make sure we don't leave a lingering invitation.
-    Invitation::take(&data.Email, &conn);
+    Invitation::take(&email, &conn);
 
     if let Some(client_kdf_iter) = data.KdfIterations {
         user.client_kdf_iter = client_kdf_iter;
diff --git a/src/api/core/organizations.rs b/src/api/core/organizations.rs
index c1d2326c..fe8dab10 100644
--- a/src/api/core/organizations.rs
+++ b/src/api/core/organizations.rs
@@ -540,18 +540,19 @@ fn send_invite(org_id: String, data: JsonUpcase<InviteData>, headers: AdminHeade
     }
 
     for email in data.Emails.iter() {
+        let email = email.to_lowercase();
         let mut user_org_status = if CONFIG.mail_enabled() {
             UserOrgStatus::Invited as i32
         } else {
             UserOrgStatus::Accepted as i32 // Automatically mark user as accepted if no email invites
         };
-        let user = match User::find_by_mail(email, &conn) {
+        let user = match User::find_by_mail(&email, &conn) {
             None => {
                 if !CONFIG.invitations_allowed() {
                     err!(format!("User does not exist: {}", email))
                 }
 
-                if !CONFIG.is_email_domain_allowed(email) {
+                if !CONFIG.is_email_domain_allowed(&email) {
                     err!("Email domain not eligible for invitations")
                 }
 
@@ -601,7 +602,7 @@ fn send_invite(org_id: String, data: JsonUpcase<InviteData>, headers: AdminHeade
             };
 
             mail::send_invite(
-                email,
+                &email,
                 &user.uuid,
                 Some(org_id.clone()),
                 Some(new_user.uuid),
diff --git a/src/db/models/user.rs b/src/db/models/user.rs
index fb7d5fcd..3c2120e1 100644
--- a/src/db/models/user.rs
+++ b/src/db/models/user.rs
@@ -73,9 +73,9 @@ impl User {
     pub const CLIENT_KDF_TYPE_DEFAULT: i32 = 0; // PBKDF2: 0
     pub const CLIENT_KDF_ITER_DEFAULT: i32 = 100_000;
 
-    pub fn new(mail: String) -> Self {
+    pub fn new(email: String) -> Self {
         let now = Utc::now().naive_utc();
-        let email = mail.to_lowercase();
+        let email = email.to_lowercase();
 
         Self {
             uuid: crate::util::get_uuid(),
@@ -349,7 +349,8 @@ impl User {
 }
 
 impl Invitation {
-    pub const fn new(email: String) -> Self {
+    pub fn new(email: String) -> Self {
+        let email = email.to_lowercase();
         Self {
             email,
         }