diff --git a/app/helpers/api/v1/inboxes_helper.rb b/app/helpers/api/v1/inboxes_helper.rb
index 3d6b559c8..8a10fa99c 100644
--- a/app/helpers/api/v1/inboxes_helper.rb
+++ b/app/helpers/api/v1/inboxes_helper.rb
@@ -17,15 +17,12 @@ module Api::V1::InboxesHelper
   def validate_imap(channel_data)
     return unless channel_data.key?('imap_enabled') && channel_data[:imap_enabled]
 
-    Mail.defaults do
-      retriever_method :imap, { address: channel_data[:imap_address],
-                                port: channel_data[:imap_port],
-                                user_name: channel_data[:imap_login],
-                                password: channel_data[:imap_password],
-                                enable_ssl: channel_data[:imap_enable_ssl] }
-    end
+    # Validate the user-selected auth mechanism before opening the connection.
+    authentication = Imap::Authentication.validate_user_configurable!(channel_data[:imap_authentication])
 
-    check_imap_connection(channel_data)
+    # Use the same auth adapter as the fetch service so LOGIN uses the IMAP LOGIN command,
+    # not SASL AUTH=LOGIN.
+    check_imap_connection(channel_data, authentication)
   end
 
   def validate_smtp(channel_data)
@@ -37,8 +34,8 @@ module Api::V1::InboxesHelper
     check_smtp_connection(channel_data, smtp)
   end
 
-  def check_imap_connection(channel_data)
-    Mail.connection {} # rubocop:disable:block
+  def check_imap_connection(channel_data, authentication)
+    imap = open_imap_connection(channel_data, authentication)
   rescue SocketError => e
     raise StandardError, I18n.t('errors.inboxes.imap.socket_error')
   rescue Net::IMAP::NoResponseError => e
@@ -53,9 +50,20 @@ module Api::V1::InboxesHelper
   rescue StandardError => e
     raise StandardError, e.message
   ensure
+    imap.disconnect if imap.present? && !imap.disconnected?
     Rails.logger.error "[Api::V1::InboxesHelper] check_imap_connection failed with #{e.message}" if e.present?
   end
 
+  def open_imap_connection(channel_data, authentication)
+    imap = build_imap_connection(channel_data)
+    Imap::Authentication.authenticate!(imap, authentication, channel_data[:imap_login], channel_data[:imap_password])
+    imap
+  end
+
+  def build_imap_connection(channel_data)
+    Net::IMAP.new(channel_data[:imap_address], port: channel_data[:imap_port], ssl: channel_data[:imap_enable_ssl])
+  end
+
   def check_smtp_connection(channel_data, smtp)
     smtp.open_timeout = 10
     smtp.start(channel_data[:smtp_domain], channel_data[:smtp_login], channel_data[:smtp_password],
diff --git a/app/javascript/dashboard/i18n/locale/en/inboxMgmt.json b/app/javascript/dashboard/i18n/locale/en/inboxMgmt.json
index 24207cef2..2620f89f7 100644
--- a/app/javascript/dashboard/i18n/locale/en/inboxMgmt.json
+++ b/app/javascript/dashboard/i18n/locale/en/inboxMgmt.json
@@ -1011,7 +1011,8 @@
         "LABEL": "Password",
         "PLACE_HOLDER": "Password"
       },
-      "ENABLE_SSL": "Enable SSL"
+      "ENABLE_SSL": "Enable SSL",
+      "AUTH_MECHANISM": "Authentication"
     },
     "MICROSOFT": {
       "TITLE": "Microsoft",
diff --git a/app/javascript/dashboard/routes/dashboard/settings/inbox/ImapSettings.vue b/app/javascript/dashboard/routes/dashboard/settings/inbox/ImapSettings.vue
index 7325793db..ab25ed1af 100644
--- a/app/javascript/dashboard/routes/dashboard/settings/inbox/ImapSettings.vue
+++ b/app/javascript/dashboard/routes/dashboard/settings/inbox/ImapSettings.vue
@@ -5,11 +5,13 @@ import SettingsFieldSection from 'dashboard/components-next/Settings/SettingsFie
 import { useVuelidate } from '@vuelidate/core';
 import { required, minLength } from '@vuelidate/validators';
 import NextButton from 'dashboard/components-next/button/Button.vue';
+import SingleSelectDropdown from './components/SingleSelectDropdown.vue';
 
 export default {
   components: {
     SettingsFieldSection,
     NextButton,
+    SingleSelectDropdown,
   },
   props: {
     inbox: {
@@ -28,6 +30,12 @@ export default {
       login: '',
       password: '',
       isSSLEnabled: true,
+      authMechanism: 'plain',
+      authMechanisms: [
+        { key: 1, value: 'plain' },
+        { key: 2, value: 'login' },
+        { key: 3, value: 'cram-md5' },
+      ],
     };
   },
   validations: {
@@ -56,6 +64,7 @@ export default {
         imap_login,
         imap_password,
         imap_enable_ssl,
+        imap_authentication,
       } = this.inbox;
       this.isIMAPEnabled = imap_enabled;
       this.address = imap_address;
@@ -63,6 +72,7 @@ export default {
       this.login = imap_login;
       this.password = imap_password;
       this.isSSLEnabled = imap_enable_ssl;
+      this.authMechanism = imap_authentication || 'plain';
     },
     async updateInbox() {
       try {
@@ -77,6 +87,7 @@ export default {
             imap_login: this.login,
             imap_password: this.password,
             imap_enable_ssl: this.isSSLEnabled,
+            imap_authentication: this.authMechanism,
           },
         };
 
@@ -90,6 +101,9 @@ export default {
         useAlert(error.message);
       }
     },
+    handleAuthMechanismChange(mode) {
+      this.authMechanism = mode;
+    },
   },
 };
 </script>
@@ -155,6 +169,13 @@ export default {
           />
           {{ $t('INBOX_MGMT.IMAP.ENABLE_SSL') }}
         </label>
+        <SingleSelectDropdown
+          class="w-full"
+          :label="$t('INBOX_MGMT.IMAP.AUTH_MECHANISM')"
+          :selected="authMechanism"
+          :options="authMechanisms"
+          :action="handleAuthMechanismChange"
+        />
       </div>
       <NextButton
         type="submit"
diff --git a/app/models/channel/email.rb b/app/models/channel/email.rb
index b1124dd75..e61123b22 100644
--- a/app/models/channel/email.rb
+++ b/app/models/channel/email.rb
@@ -6,6 +6,7 @@
 #  email                     :string           not null
 #  forward_to_email          :string           not null
 #  imap_address              :string           default("")
+#  imap_authentication       :string           default("plain")
 #  imap_enable_ssl           :boolean          default(TRUE)
 #  imap_enabled              :boolean          default(FALSE)
 #  imap_login                :string           default("")
@@ -47,7 +48,7 @@ class Channel::Email < ApplicationRecord
   end
 
   self.table_name = 'channel_email'
-  EDITABLE_ATTRS = [:email, :imap_enabled, :imap_login, :imap_password, :imap_address, :imap_port, :imap_enable_ssl,
+  EDITABLE_ATTRS = [:email, :imap_enabled, :imap_login, :imap_password, :imap_address, :imap_port, :imap_enable_ssl, :imap_authentication,
                     :smtp_enabled, :smtp_login, :smtp_password, :smtp_address, :smtp_port, :smtp_domain, :smtp_enable_starttls_auto,
                     :smtp_enable_ssl_tls, :smtp_openssl_verify_mode, :smtp_authentication, :provider, :verified_for_sending].freeze
 
diff --git a/app/services/imap/authentication.rb b/app/services/imap/authentication.rb
new file mode 100644
index 000000000..d5eb17cdd
--- /dev/null
+++ b/app/services/imap/authentication.rb
@@ -0,0 +1,31 @@
+module Imap::Authentication
+  DEFAULT_MECHANISM = 'plain'.freeze
+  USER_CONFIGURABLE_MECHANISMS = %w[plain login cram-md5].freeze
+
+  module_function
+
+  def normalize(mechanism)
+    mechanism.presence || DEFAULT_MECHANISM
+  end
+
+  def validate_user_configurable!(mechanism)
+    normalized_mechanism = normalize(mechanism).to_s.downcase
+    return normalized_mechanism if USER_CONFIGURABLE_MECHANISMS.include?(normalized_mechanism)
+
+    allowed_values = USER_CONFIGURABLE_MECHANISMS.join(', ')
+    raise StandardError, "Invalid IMAP authentication mechanism. Allowed values: #{allowed_values}"
+  end
+
+  def authenticate!(imap, mechanism, username, password)
+    normalized_mechanism = normalize(mechanism).to_s.downcase
+
+    case normalized_mechanism
+    when 'cram-md5'
+      imap.authenticate('CRAM-MD5', username, password)
+    when 'login'
+      imap.login(username, password)
+    else
+      imap.authenticate(normalize(mechanism), username, password)
+    end
+  end
+end
diff --git a/app/services/imap/base_fetch_email_service.rb b/app/services/imap/base_fetch_email_service.rb
index 17114f516..5a6d3537c 100644
--- a/app/services/imap/base_fetch_email_service.rb
+++ b/app/services/imap/base_fetch_email_service.rb
@@ -130,8 +130,9 @@ class Imap::BaseFetchEmailService
   end
 
   def build_imap_client
-    imap = Net::IMAP.new(channel.imap_address, port: channel.imap_port, ssl: true)
-    imap.authenticate(authentication_type, channel.imap_login, imap_password)
+    imap = Net::IMAP.new(channel.imap_address, port: channel.imap_port, ssl: channel.imap_enable_ssl)
+    Imap::Authentication.authenticate!(imap, authentication_type, channel.imap_login, imap_password)
+
     imap.select('INBOX')
     imap
   end
diff --git a/app/services/imap/fetch_email_service.rb b/app/services/imap/fetch_email_service.rb
index f602b3375..2fa389e31 100644
--- a/app/services/imap/fetch_email_service.rb
+++ b/app/services/imap/fetch_email_service.rb
@@ -6,7 +6,7 @@ class Imap::FetchEmailService < Imap::BaseFetchEmailService
   private
 
   def authentication_type
-    'PLAIN'
+    channel.imap_authentication || 'plain'
   end
 
   def imap_password
diff --git a/app/views/api/v1/models/_inbox.json.jbuilder b/app/views/api/v1/models/_inbox.json.jbuilder
index e4c19fea0..3da71d07d 100644
--- a/app/views/api/v1/models/_inbox.json.jbuilder
+++ b/app/views/api/v1/models/_inbox.json.jbuilder
@@ -90,6 +90,7 @@ if resource.email?
     json.imap_port resource.channel.try(:imap_port)
     json.imap_enabled resource.channel.try(:imap_enabled)
     json.imap_enable_ssl resource.channel.try(:imap_enable_ssl)
+    json.imap_authentication resource.channel.try(:imap_authentication)
 
     if resource.channel.try(:microsoft?) || resource.channel.try(:google?) || resource.channel.try(:legacy_google?)
       json.reauthorization_required resource.channel.try(:provider_config).empty? || resource.channel.try(:reauthorization_required?)
diff --git a/db/migrate/20260507000000_add_imap_authentication_to_channel_email.rb b/db/migrate/20260507000000_add_imap_authentication_to_channel_email.rb
new file mode 100644
index 000000000..ffdf94bf2
--- /dev/null
+++ b/db/migrate/20260507000000_add_imap_authentication_to_channel_email.rb
@@ -0,0 +1,5 @@
+class AddImapAuthenticationToChannelEmail < ActiveRecord::Migration[7.0]
+  def change
+    add_column :channel_email, :imap_authentication, :string, default: 'plain'
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index f7c3cce6d..9f8d76b78 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[7.1].define(version: 2026_04_30_114500) do
+ActiveRecord::Schema[7.1].define(version: 2026_05_07_000000) do
   # These extensions should be enabled to support this database
   enable_extension "pg_stat_statements"
   enable_extension "pg_trgm"
@@ -472,6 +472,7 @@ ActiveRecord::Schema[7.1].define(version: 2026_04_30_114500) do
     t.boolean "smtp_enable_ssl_tls", default: false
     t.jsonb "provider_config", default: {}
     t.string "provider"
+    t.string "imap_authentication", default: "plain"
     t.boolean "verified_for_sending", default: false, null: false
     t.index ["email"], name: "index_channel_email_on_email", unique: true
     t.index ["forward_to_email"], name: "index_channel_email_on_forward_to_email", unique: true
diff --git a/spec/controllers/api/v1/accounts/inboxes_controller_spec.rb b/spec/controllers/api/v1/accounts/inboxes_controller_spec.rb
index 8aae60d53..0372bb141 100644
--- a/spec/controllers/api/v1/accounts/inboxes_controller_spec.rb
+++ b/spec/controllers/api/v1/accounts/inboxes_controller_spec.rb
@@ -568,8 +568,10 @@ RSpec.describe 'Inboxes API', type: :request do
         email_channel = create(:channel_email, account: account)
         email_inbox = create(:inbox, channel: email_channel, account: account)
 
-        imap_connection = double
-        allow(Mail).to receive(:connection).and_return(imap_connection)
+        imap_connection = instance_double(Net::IMAP, disconnected?: false)
+        allow(Net::IMAP).to receive(:new).and_return(imap_connection)
+        allow(imap_connection).to receive(:login)
+        allow(imap_connection).to receive(:disconnect)
 
         patch "/api/v1/accounts/#{account.id}/inboxes/#{email_inbox.id}",
               headers: admin.create_new_auth_token,
@@ -578,7 +580,8 @@ RSpec.describe 'Inboxes API', type: :request do
                   imap_enabled: true,
                   imap_address: 'imap.gmail.com',
                   imap_port: 993,
-                  imap_login: 'imaptest@gmail.com'
+                  imap_login: 'imaptest@gmail.com',
+                  imap_authentication: 'login'
                 }
               },
               as: :json
@@ -587,6 +590,7 @@ RSpec.describe 'Inboxes API', type: :request do
         expect(email_channel.reload.imap_enabled).to be true
         expect(email_channel.reload.imap_address).to eq('imap.gmail.com')
         expect(email_channel.reload.imap_port).to eq(993)
+        expect(email_channel.reload.imap_authentication).to eq('login')
       end
 
       it 'updates avatar when administrator' do
diff --git a/spec/factories/channel/channel_email.rb b/spec/factories/channel/channel_email.rb
index 32cdb0488..516699594 100644
--- a/spec/factories/channel/channel_email.rb
+++ b/spec/factories/channel/channel_email.rb
@@ -16,6 +16,7 @@ FactoryBot.define do
       imap_login { 'email@example.com' }
       imap_password { '' }
       imap_enable_ssl { true }
+
       provider_config do
         {
           expires_on: Time.zone.now + 3600,
@@ -33,6 +34,7 @@ FactoryBot.define do
       imap_login { 'email@example.com' }
       imap_password { 'random-password' }
       imap_enable_ssl { true }
+      imap_authentication { 'plain' }
     end
   end
 end
diff --git a/spec/services/imap/fetch_email_service_spec.rb b/spec/services/imap/fetch_email_service_spec.rb
index 2910f41fb..a40a46343 100644
--- a/spec/services/imap/fetch_email_service_spec.rb
+++ b/spec/services/imap/fetch_email_service_spec.rb
@@ -13,14 +13,68 @@ RSpec.describe Imap::FetchEmailService do
     before do
       allow(Rails).to receive(:logger).and_return(logger)
       allow(Net::IMAP).to receive(:new).with(
-        imap_email_channel.imap_address, port: imap_email_channel.imap_port, ssl: true
+        imap_email_channel.imap_address, port: imap_email_channel.imap_port, ssl: imap_email_channel.imap_enable_ssl
       ).and_return(imap)
       allow(imap).to receive(:authenticate).with(
-        'PLAIN', imap_email_channel.imap_login, imap_email_channel.imap_password
+        'plain', imap_email_channel.imap_login, imap_email_channel.imap_password
       )
       allow(imap).to receive(:select).with('INBOX')
     end
 
+    context 'when using CRAM-MD5 authentication' do
+      let(:cram_md5_channel) { create(:channel_email, :imap_email, account: account, imap_authentication: 'cram-md5') }
+
+      before do
+        allow(Net::IMAP).to receive(:new).with(
+          cram_md5_channel.imap_address, port: cram_md5_channel.imap_port, ssl: cram_md5_channel.imap_enable_ssl
+        ).and_return(imap)
+        allow(imap).to receive(:authenticate).with(
+          'CRAM-MD5', cram_md5_channel.imap_login, cram_md5_channel.imap_password
+        )
+        allow(imap).to receive(:select).with('INBOX')
+      end
+
+      it 'uses CRAM-MD5 authentication' do
+        travel_to '26.10.2020 10:00'.to_datetime do
+          allow(imap).to receive(:search).with(%w[SINCE 25-Oct-2020]).and_return([])
+          allow(imap).to receive(:logout)
+
+          described_class.new(channel: cram_md5_channel).perform
+
+          expect(imap).to have_received(:authenticate).with(
+            'CRAM-MD5', cram_md5_channel.imap_login, cram_md5_channel.imap_password
+          )
+        end
+      end
+    end
+
+    context 'when using LOGIN authentication' do
+      let(:login_channel) { create(:channel_email, :imap_email, account: account, imap_authentication: 'login') }
+
+      before do
+        allow(Net::IMAP).to receive(:new).with(
+          login_channel.imap_address, port: login_channel.imap_port, ssl: login_channel.imap_enable_ssl
+        ).and_return(imap)
+        allow(imap).to receive(:login).with(
+          login_channel.imap_login, login_channel.imap_password
+        )
+        allow(imap).to receive(:select).with('INBOX')
+      end
+
+      it 'uses LOGIN authentication' do
+        travel_to '26.10.2020 10:00'.to_datetime do
+          allow(imap).to receive(:search).with(%w[SINCE 25-Oct-2020]).and_return([])
+          allow(imap).to receive(:logout)
+
+          described_class.new(channel: login_channel).perform
+
+          expect(imap).to have_received(:login).with(
+            login_channel.imap_login, login_channel.imap_password
+          )
+        end
+      end
+    end
+
     context 'when new emails are available in the mailbox' do
       it 'fetches the emails and returns the emails that are not present in the db' do
         travel_to '26.10.2020 10:00'.to_datetime do