diff --git a/CHANGELOG.md b/CHANGELOG.md
index e5142ab2b..2fdc1a7e0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,7 @@ nav_order: 1
 ## [X.Y.Z] - YYYY-MM-DD
 
 - Fix incorrect read context in MySQL user resource
+- Add validation for email fields in `account_team_member`, `organization_user` and `project_user` resources to check if email is lowercase and valid
 
 ## [3.13.4] - 2023-09-28
 
diff --git a/docs/data-sources/account_team_member.md b/docs/data-sources/account_team_member.md
index cf6ba4121..5f07979ac 100644
--- a/docs/data-sources/account_team_member.md
+++ b/docs/data-sources/account_team_member.md
@@ -27,7 +27,7 @@ data "aiven_account_team_member" "foo" {
 
 - `account_id` (String) The unique account id This property cannot be changed, doing so forces recreation of the resource.
 - `team_id` (String) An account team id This property cannot be changed, doing so forces recreation of the resource.
-- `user_email` (String) Is a user email address that first will be invited, and after accepting an invitation, he or she becomes a member of a team. This property cannot be changed, doing so forces recreation of the resource.
+- `user_email` (String) Is a user email address that first will be invited, and after accepting an invitation, he or she becomes a member of a team. Should be lowercase.
 
 ### Read-Only
 
diff --git a/docs/data-sources/project_user.md b/docs/data-sources/project_user.md
index f706c30e6..70326172a 100644
--- a/docs/data-sources/project_user.md
+++ b/docs/data-sources/project_user.md
@@ -24,7 +24,7 @@ data "aiven_project_user" "mytestuser" {
 
 ### Required
 
-- `email` (String) Email address of the user. This property cannot be changed, doing so forces recreation of the resource.
+- `email` (String) Email address of the user. Should be lowercase
 - `project` (String) Identifies the project this resource belongs to. To set up proper dependencies please refer to this variable as a reference. This property cannot be changed, doing so forces recreation of the resource.
 
 ### Read-Only
diff --git a/docs/resources/account_team_member.md b/docs/resources/account_team_member.md
index 87a493ab9..8784f5077 100644
--- a/docs/resources/account_team_member.md
+++ b/docs/resources/account_team_member.md
@@ -38,7 +38,7 @@ resource "aiven_account_team_member" "foo" {
 
 - `account_id` (String) The unique account id This property cannot be changed, doing so forces recreation of the resource.
 - `team_id` (String) An account team id This property cannot be changed, doing so forces recreation of the resource.
-- `user_email` (String) Is a user email address that first will be invited, and after accepting an invitation, he or she becomes a member of a team. This property cannot be changed, doing so forces recreation of the resource.
+- `user_email` (String) Is a user email address that first will be invited, and after accepting an invitation, he or she becomes a member of a team. Should be lowercase.
 
 ### Optional
 
diff --git a/docs/resources/project_user.md b/docs/resources/project_user.md
index b3ab8e863..2fa6d986b 100644
--- a/docs/resources/project_user.md
+++ b/docs/resources/project_user.md
@@ -25,7 +25,7 @@ resource "aiven_project_user" "mytestuser" {
 
 ### Required
 
-- `email` (String) Email address of the user. This property cannot be changed, doing so forces recreation of the resource.
+- `email` (String) Email address of the user. Should be lowercase
 - `member_type` (String) Project membership type. The possible values are `admin`, `developer` and `operator`.
 - `project` (String) Identifies the project this resource belongs to. To set up proper dependencies please refer to this variable as a reference. This property cannot be changed, doing so forces recreation of the resource.
 
diff --git a/go.mod b/go.mod
index 33b05442c..fa521e68e 100644
--- a/go.mod
+++ b/go.mod
@@ -1,6 +1,6 @@
 module github.com/aiven/terraform-provider-aiven
 
-go 1.18
+go 1.21
 
 require (
 	github.com/aiven/aiven-go-client v1.7.1-0.20230208122034-270adff994ec
diff --git a/go.sum b/go.sum
index a32aa8f0f..0d1e43121 100644
--- a/go.sum
+++ b/go.sum
@@ -60,6 +60,7 @@ github.com/apparentlymart/go-cidr v1.1.0 h1:2mAhrMoF+nhXqxTzSZMUzDHkLjmIHC+Zzn4t
 github.com/apparentlymart/go-cidr v1.1.0/go.mod h1:EBcsNrHc3zQeuaeCeCtQruQm+n9/YjEn/vI25Lg7Gwc=
 github.com/apparentlymart/go-dump v0.0.0-20180507223929-23540a00eaa3/go.mod h1:oL81AME2rN47vu18xqj1S1jPIPuN7afo62yKTNn3XMM=
 github.com/apparentlymart/go-dump v0.0.0-20190214190832-042adf3cf4a0 h1:MzVXffFUye+ZcSR6opIgz9Co7WcDx6ZcY+RjfFHoA0I=
+github.com/apparentlymart/go-dump v0.0.0-20190214190832-042adf3cf4a0/go.mod h1:oL81AME2rN47vu18xqj1S1jPIPuN7afo62yKTNn3XMM=
 github.com/apparentlymart/go-textseg v1.0.0/go.mod h1:z96Txxhf3xSFMPmb5X/1W05FF/Nj9VFpLOpjS5yuumk=
 github.com/apparentlymart/go-textseg/v12 v12.0.0/go.mod h1:S/4uRK2UtaQttw1GenVJEynmyUenKwP++x/+DdGV/Ec=
 github.com/apparentlymart/go-textseg/v13 v13.0.0 h1:Y+KvPE1NYz0xl601PVImeQfFyEy6iT90AvPUL1NNfNw=
@@ -105,6 +106,7 @@ github.com/fatih/color v1.13.0 h1:8LOYc1KYPPmyKMuN8QV2DNRWNbLo6LZ0iLs8+mlH53w=
 github.com/fatih/color v1.13.0/go.mod h1:kLAiJbzzSOZDVNGyDpeOxJ47H46qBXwg5ILebYFFOfk=
 github.com/flynn/go-shlex v0.0.0-20150515145356-3f9db97f8568/go.mod h1:xEzjJPgXI435gkrCt3MPfRiAkVrwSbHsst4LCFVfpJc=
 github.com/fsnotify/fsnotify v1.5.4 h1:jRbGcIw6P2Meqdwuo0H1p6JVLbL5DHKAKlYndzMwVZI=
+github.com/fsnotify/fsnotify v1.5.4/go.mod h1:OVB6XrOHzAwXMpEM7uPOzcehqUV2UqJxmVXmkdnm1bU=
 github.com/gliderlabs/ssh v0.2.2/go.mod h1:U7qILu1NlMHj9FlMhZLlkCdDnU1DBEAqr0aevW3Awn0=
 github.com/go-git/gcfg v1.5.0 h1:Q5ViNfGF8zFgyJWPqYwA7qGFoMTEiBmdlkcfRmpIMa4=
 github.com/go-git/gcfg v1.5.0/go.mod h1:5m20vg6GwYabIxaOonVkTdrILxQMpEShl1xiMF4ua+E=
@@ -258,6 +260,7 @@ github.com/jbenet/go-context v0.0.0-20150711004518-d14ea06fba99 h1:BQSFePA1RWJOl
 github.com/jbenet/go-context v0.0.0-20150711004518-d14ea06fba99/go.mod h1:1lJo3i6rXxKeerYnT8Nvf0QmHCRC1n8sfWVwXF2Frvo=
 github.com/jessevdk/go-flags v1.5.0/go.mod h1:Fw0T6WPc1dYxT4mKEZRfG5kJhaTDP9pj1c2EWnYs/m4=
 github.com/jhump/protoreflect v1.6.0 h1:h5jfMVslIg6l29nsMs0D8Wj17RDVdNYti0vDN/PZZoE=
+github.com/jhump/protoreflect v1.6.0/go.mod h1:eaTn3RZAmMBcV0fifFvlm6VHNz3wSkYyXYWUh7ymB74=
 github.com/jinzhu/copier v0.0.0-20190924061706-b57f9002281a h1:zPPuIq2jAWWPTrGt70eK/BSch+gFAGrNzecsoENgu2o=
 github.com/jinzhu/copier v0.0.0-20190924061706-b57f9002281a/go.mod h1:yL958EeXv8Ylng6IfnvG4oflryUi3vgA3xPs9hmII1s=
 github.com/jmespath/go-jmespath v0.0.0-20160202185014-0b12d6b521d8/go.mod h1:Nht3zPeWKUH0NzdCt2Blrr5ys8VGpn0CEB0cQHVjt7k=
@@ -280,6 +283,7 @@ github.com/konsorten/go-windows-terminal-sequences v1.0.1/go.mod h1:T0+1ngSBFLxv
 github.com/kr/pretty v0.1.0/go.mod h1:dAy3ld7l9f0ibDNOQOHHMYYIIbhfbHSm3C4ZsoJORNo=
 github.com/kr/pretty v0.2.1/go.mod h1:ipq/a2n7PKx3OHsz4KJII5eveXtPO4qwEXGdVfWzfnI=
 github.com/kr/pretty v0.3.0 h1:WgNl7dwNpEZ6jJ9k1snq4pZsg7DOEN8hP9Xw0Tsjwk0=
+github.com/kr/pretty v0.3.0/go.mod h1:640gp4NfQd8pI5XOwp5fnNeVWj67G7CFk/SaSQn7NBk=
 github.com/kr/pty v1.1.1/go.mod h1:pFQYn66WHrOpPYNljwOMqo10TkYh1fy3cYio2l3bCsQ=
 github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
 github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
@@ -316,11 +320,15 @@ github.com/mitchellh/reflectwalk v1.0.2 h1:G2LzWKi524PWgd3mLHV8Y5k7s6XUvT0Gef6zx
 github.com/mitchellh/reflectwalk v1.0.2/go.mod h1:mSTlrgnPZtwu0c4WaC2kGObEpuNDbx0jmZXqmk4esnw=
 github.com/niemeyer/pretty v0.0.0-20200227124842-a10e7caefd8e/go.mod h1:zD1mROLANZcx1PVRCS0qkT7pwLkGfwJo4zjcN/Tysno=
 github.com/nsf/jsondiff v0.0.0-20200515183724-f29ed568f4ce h1:RPclfga2SEJmgMmz2k+Mg7cowZ8yv4Trqw9UsJby758=
+github.com/nsf/jsondiff v0.0.0-20200515183724-f29ed568f4ce/go.mod h1:uFMI8w+ref4v2r9jz+c9i1IfIttS/OkmLfrk1jne5hs=
 github.com/nxadm/tail v1.4.8 h1:nPr65rt6Y5JFSKQO7qToXr7pePgD6Gwiw05lkbyAQTE=
+github.com/nxadm/tail v1.4.8/go.mod h1:+ncqLTQzXmGhMZNUePPaPqPvBxHAIsmXswZKocGu+AU=
 github.com/oklog/run v1.1.0 h1:GEenZ1cK0+q0+wsJew9qUg/DyD8k3JzYsZAi5gYi2mA=
 github.com/oklog/run v1.1.0/go.mod h1:sVPdnTZT1zYwAJeCMu2Th4T21pA3FPOQRfWjQlk7DVU=
 github.com/onsi/ginkgo v1.16.5 h1:8xi0RTUf59SOSfEtZMvwTvXYMzG4gV23XVHOZiXNtnE=
+github.com/onsi/ginkgo v1.16.5/go.mod h1:+E8gABHa3K6zRBolWtd+ROzc/U5bkGt0FwiG042wbpU=
 github.com/onsi/gomega v1.19.0 h1:4ieX6qQjPP/BfC3mpsAtIGGlxTWPeA3Inl/7DtXw1tw=
+github.com/onsi/gomega v1.19.0/go.mod h1:LY+I3pBVzYsTBU1AnDwOSxaYi9WoWiqgwooUqq9yPro=
 github.com/pkg/errors v0.8.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
@@ -333,6 +341,7 @@ github.com/sebdah/goldie v1.0.0/go.mod h1:jXP4hmWywNEwZzhMuv2ccnqTSFpuq8iyQhtQdk
 github.com/sergi/go-diff v1.0.0/go.mod h1:0CfEIISq7TuYL3j771MWULgwwjU+GofnZX9QAmXWZgo=
 github.com/sergi/go-diff v1.1.0/go.mod h1:STckp+ISIX8hZLjrqAeVduY0gWCT9IjLuqbuNXdaHfM=
 github.com/sergi/go-diff v1.2.0 h1:XU+rvMAioB0UC3q1MFrIQy4Vo5/4VsRDQQXHsEya6xQ=
+github.com/sergi/go-diff v1.2.0/go.mod h1:STckp+ISIX8hZLjrqAeVduY0gWCT9IjLuqbuNXdaHfM=
 github.com/sirupsen/logrus v1.4.1/go.mod h1:ni0Sbl8bgC9z8RoU9G6nDWqqs/fq4eDPysMBDgk/93Q=
 github.com/spf13/pflag v1.0.2/go.mod h1:DYY7MBk1bdzusC3SYhjObp+wFpr4gzcvqqNjLnInEg4=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
@@ -556,6 +565,7 @@ golang.org/x/sys v0.0.0-20220817070843-5a390386f1f2 h1:fqTvyMIIj+HRzMmnzr9NtpHP6
 golang.org/x/sys v0.0.0-20220817070843-5a390386f1f2/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
 golang.org/x/term v0.0.0-20210927222741-03fcf44c2211 h1:JGgROgKl9N8DuW20oFS5gxc+lE67/N3FcwmBPMe7ArY=
+golang.org/x/term v0.0.0-20210927222741-03fcf44c2211/go.mod h1:jbD1KX2456YbFQfuXm/mYQcufACuNUgVhRMnK/tPxf8=
 golang.org/x/text v0.0.0-20170915032832-14c0d48ead0c/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.1-0.20180807135948-17ff2d5776d2/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
@@ -745,6 +755,7 @@ gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c/go.mod h1:JHkPIbrfpd72SG/EV
 gopkg.in/cheggaaa/pb.v1 v1.0.27/go.mod h1:V/YB90LKu/1FcN3WVnfiiE5oMCibMjukxqG/qStrOgw=
 gopkg.in/errgo.v2 v2.1.0/go.mod h1:hNsd1EY+bozCKY1Ytp96fpM3vjJbqLJn88ws8XvfDNI=
 gopkg.in/tomb.v1 v1.0.0-20141024135613-dd632973f1e7 h1:uRGJdciOHaEIrze2W8Q3AKkepLTh2hOroT7a+7czfdQ=
+gopkg.in/tomb.v1 v1.0.0-20141024135613-dd632973f1e7/go.mod h1:dt/ZhP58zS4L8KSrWDmTeBkI65Dw0HsyUHuEVlX15mw=
 gopkg.in/warnings.v0 v0.1.2 h1:wFXVbFY8DY5/xOe1ECiWdKCzZlxgshcYVNkBHstARME=
 gopkg.in/warnings.v0 v0.1.2/go.mod h1:jksf8JmL6Qr/oQM2OXTHunEvvTAsrWBLb6OOjuVWRNI=
 gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
@@ -752,6 +763,7 @@ gopkg.in/yaml.v2 v2.2.4/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v2 v2.2.8/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v2 v2.3.0/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v2 v2.4.0 h1:D8xgwECY7CYvx+Y2n4sBz93Jn9JRvxdiyyo8CTfuKaY=
+gopkg.in/yaml.v2 v2.4.0/go.mod h1:RDklbk79AGWmwhnvt/jBztapEOGDOx6ZbXqjP6csGnQ=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
diff --git a/internal/schemautil/schemautil.go b/internal/schemautil/schemautil.go
index 9f3ae313f..56c34a639 100644
--- a/internal/schemautil/schemautil.go
+++ b/internal/schemautil/schemautil.go
@@ -2,6 +2,7 @@ package schemautil
 
 import (
 	"fmt"
+	"net/mail"
 	"net/url"
 	"regexp"
 	"strconv"
@@ -349,3 +350,19 @@ func unmarshalUserConfig(src interface{}) ([]map[string]interface{}, error) {
 
 	return []map[string]interface{}{config}, nil
 }
+
+// ValidateEmailAddress is a ValidateFunc that ensures a string is a valid email address
+func ValidateEmailAddress(v any, k string) (ws []string, errors []error) {
+	addr, err := mail.ParseAddress(v.(string))
+	if err != nil {
+		errors = append(errors, err)
+
+		return
+	}
+
+	if strings.ToLower(addr.Address) != addr.Address {
+		errors = append(errors, fmt.Errorf("%q: invalid email address", k))
+	}
+
+	return
+}
diff --git a/internal/service/account/account_team_member.go b/internal/service/account/account_team_member.go
index c04d5f95f..4d04807af 100644
--- a/internal/service/account/account_team_member.go
+++ b/internal/service/account/account_team_member.go
@@ -25,10 +25,12 @@ var aivenAccountTeamMemberSchema = map[string]*schema.Schema{
 		Description: schemautil.Complex("An account team id").ForceNew().Build(),
 	},
 	"user_email": {
-		Type:        schema.TypeString,
-		Required:    true,
-		ForceNew:    true,
-		Description: schemautil.Complex("Is a user email address that first will be invited, and after accepting an invitation, he or she becomes a member of a team.").ForceNew().Build(),
+		Type:     schema.TypeString,
+		Required: true,
+		ForceNew: true,
+		Description: "Is a user email address that first will be invited, and after accepting an invitation, he " +
+			"or she becomes a member of a team. Should be lowercase.",
+		ValidateFunc: schemautil.ValidateEmailAddress,
 	},
 	"invited_by_user_email": {
 		Type:        schema.TypeString,
diff --git a/internal/service/project/project_user.go b/internal/service/project/project_user.go
index 0168ccae3..e1554a987 100644
--- a/internal/service/project/project_user.go
+++ b/internal/service/project/project_user.go
@@ -14,10 +14,11 @@ import (
 var aivenProjectUserSchema = map[string]*schema.Schema{
 	"project": schemautil.CommonSchemaProjectReference,
 	"email": {
-		ForceNew:    true,
-		Required:    true,
-		Type:        schema.TypeString,
-		Description: schemautil.Complex("Email address of the user.").ForceNew().Build(),
+		ForceNew:     true,
+		Required:     true,
+		Type:         schema.TypeString,
+		Description:  "Email address of the user. Should be lowercase",
+		ValidateFunc: schemautil.ValidateEmailAddress,
 	},
 	"member_type": {
 		Required:    true,