diff --git a/lib/letter-avatars.ts b/lib/letter-avatars.ts
index 3d038047b..e476ad6bb 100644
--- a/lib/letter-avatars.ts
+++ b/lib/letter-avatars.ts
@@ -25,9 +25,6 @@ export function generateAvatar (name: string): string {
 
 export function generateAvatarURL (name: string, email = '', big = true): string {
   let photo
-  if (email.length === 0) {
-    email = '' + name + '@example.com'
-  }
   name = encodeURIComponent(name)
 
   const hash = createHash('md5')
diff --git a/lib/models/user.ts b/lib/models/user.ts
index 69d08f19e..453379cf7 100644
--- a/lib/models/user.ts
+++ b/lib/models/user.ts
@@ -36,7 +36,7 @@ export type Profile = {
   id: string;
   username: string;
   displayName: string;
-  emails: any[];
+  emails: string[];
   avatarUrl: string;
   profileUrl: string;
   provider: ProviderEnum;
@@ -125,7 +125,7 @@ export class User extends Model<User> {
         }
         break
       case ProviderEnum.dropbox:
-        photo = generateAvatarURL('', profile.emails[0].value, bigger)
+        photo = generateAvatarURL('', profile.emails[0], bigger)
         break
       case ProviderEnum.google:
         photo = profile.photos[0].value
diff --git a/lib/web/auth/dropbox/index.ts b/lib/web/auth/dropbox/index.ts
index 0ed3c7324..bf8db04a6 100644
--- a/lib/web/auth/dropbox/index.ts
+++ b/lib/web/auth/dropbox/index.ts
@@ -1,7 +1,8 @@
 import { NextFunction, Request, Response, Router } from 'express'
 import passport from 'passport'
-import * as DropboxStrategy from 'passport-dropbox-oauth2'
+import { Strategy as DropboxStrategy } from 'passport-dropbox-oauth2'
 import { config } from '../../../config'
+import { User } from '../../../models'
 import { AuthMiddleware } from '../interface'
 import { passportGeneralCallback } from '../utils'
 
@@ -14,7 +15,17 @@ export const DropboxMiddleware: AuthMiddleware = {
       clientID: config.dropbox.clientID,
       clientSecret: config.dropbox.clientSecret,
       callbackURL: config.serverURL + '/auth/dropbox/callback'
-    }, passportGeneralCallback))
+    }, (
+      accessToken: string,
+      refreshToken: string,
+      profile: any,
+      done: (err?: Error | null, user?: User) => void
+    ): void => {
+      // the Dropbox plugin wraps the email addresses in an object
+      // see https://github.com/florianheinemann/passport-dropbox-oauth2/blob/master/lib/passport-dropbox-oauth2/strategy.js#L146
+      profile.emails = profile.emails.map(element => element.value)
+      passportGeneralCallback(accessToken, refreshToken, profile, done)
+    }))
 
     dropboxAuth.get('/auth/dropbox', function (req: Request, res: Response, next: NextFunction) {
       passport.authenticate('dropbox-oauth2')(req, res, next)
diff --git a/test/auth.ts b/test/auth.ts
new file mode 100644
index 000000000..334206307
--- /dev/null
+++ b/test/auth.ts
@@ -0,0 +1,110 @@
+import assert from 'assert'
+import { ImportMock } from 'ts-mock-imports'
+import * as configModule from '../lib/config'
+import { DropboxMiddleware } from '../lib/web/auth/dropbox'
+import { EmailMiddleware } from '../lib/web/auth/email'
+import { FacebookMiddleware } from '../lib/web/auth/facebook'
+import { GithubMiddleware } from '../lib/web/auth/github'
+import { GitlabMiddleware } from '../lib/web/auth/gitlab'
+import { GoogleMiddleware } from '../lib/web/auth/google'
+import { LdapMiddleware } from '../lib/web/auth/ldap'
+import { OAuth2Middleware } from '../lib/web/auth/oauth2'
+import { OPenIDMiddleware } from '../lib/web/auth/openid'
+import { TwitterMiddleware } from '../lib/web/auth/twitter'
+
+describe('AuthMiddlewares', function () {
+  // We currently exclude the SAML Auth, because it needs a certificate file
+  const middlewareList = [{
+    name: 'Facebook',
+    middleware: FacebookMiddleware,
+    config: {
+      facebook: {
+        clientID: 'foobar',
+        clientSecret: 'foobar'
+      }
+    }
+  }, {
+    name: 'Twitter',
+    middleware: TwitterMiddleware,
+    config: {
+      twitter: {
+        consumerKey: 'foobar',
+        consumerSecret: 'foobar'
+      }
+    }
+  }, {
+    name: 'GitHub',
+    middleware: GithubMiddleware,
+    config: {
+      github: {
+        clientID: 'foobar',
+        clientSecret: 'foobar'
+      }
+    }
+  }, {
+    name: 'Gitlab',
+    middleware: GitlabMiddleware,
+    config: {
+      gitlab: {
+        clientID: 'foobar',
+        clientSecret: 'foobar'
+      }
+    }
+  }, {
+    name: 'Dropbox',
+    middleware: DropboxMiddleware,
+    config: {
+      dropbox: {
+        clientID: 'foobar',
+        clientSecret: 'foobar'
+      }
+    }
+  }, {
+    name: 'Google',
+    middleware: GoogleMiddleware,
+    config: {
+      google: {
+        clientID: 'foobar',
+        clientSecret: 'foobar'
+      }
+    }
+  }, {
+    name: 'LDAP',
+    middleware: LdapMiddleware,
+    config: {
+      ldap: {}
+    }
+  }, {
+    name: 'OAuth2',
+    middleware: OAuth2Middleware,
+    config: {
+      oauth2: {
+        clientID: 'foobar',
+        clientSecret: 'foobar',
+        authorizationURL: 'foobar',
+        tokenURL: 'foobar',
+        userProfileURL: 'foobar',
+        scope: 'foobar'
+      }
+    }
+  }, {
+    name: 'Email',
+    middleware: EmailMiddleware,
+    config: {}
+  }, {
+    name: 'OpenID',
+    middleware: OPenIDMiddleware,
+    config: {}
+  }]
+
+  middlewareList.forEach((middleware) => {
+    describe(middleware.name + 'Middleware', () => {
+      before(() => {
+        ImportMock.mockOther(configModule, 'config', middleware.config)
+      })
+      it('can be instantiated', () => {
+        assert.ok(middleware.middleware.getMiddleware())
+      })
+    })
+  })
+})