Can't use Brevo (sendinblue) SMTP service in Nextcloud, but can use in other services

Support intro

Nextcloud version (eg, 20.0.5): Nextcloud Hub 5 (27.0.1)
Operating system and version (eg, Ubuntu 20.04): Ubuntu 22.04 (running Nextcloud using the official Docker Image)
PHP version (eg, 7.4): 8.2.8

The issue you are facing:

Is this the first time you’ve seen this error? (Y/N): n

Steps to replicate it:

  1. FIll out all the boxes in Administration > Basic Settings > Email server
  2. Clicking ‘Send email’

The output of your Nextcloud log in Admin > Logging:

Error	index	Horde_Imap_Client_Exception: Authentication failed.
/var/www/html/custom_apps/mail/vendor/bytestream/horde-imap-client/lib/Horde/Imap/Client/Socket.php - line 4566:

Horde_Imap_Client_Socket->_responseCode([ "Horde_Ima ... ]], [ "Horde_Ima ... "])

/var/www/html/custom_apps/mail/vendor/bytestream/horde-imap-client/lib/Horde/Imap/Client/Socket.php - line 4314:

Horde_Imap_Client_Socket->_getLine([ "Horde_Ima ... ]])

/var/www/html/custom_apps/mail/vendor/bytestream/horde-imap-client/lib/Horde/Imap/Client/Socket.php - line 4242:

Horde_Imap_Client_Socket->_sendCmdChunk([ "Horde_Ima ... ]], [ [ "Horde_I ... ]])

/var/www/html/custom_apps/mail/vendor/bytestream/horde-imap-client/lib/Horde/Imap/Client/Socket.php - line 850:

Horde_Imap_Client_Socket->_sendCmd([ "Horde_Ima ... ]])

/var/www/html/custom_apps/mail/vendor/bytestream/horde-imap-client/lib/Horde/Imap/Client/Socket.php - line 512:

Horde_Imap_Client_Socket->_tryLogin("*** sensiti ... *")

/var/www/html/custom_apps/mail/vendor/bytestream/horde-imap-client/lib/Horde/Imap/Client/Base.php - line 853:

Horde_Imap_Client_Socket->_login("*** sensiti ... *")

/var/www/html/custom_apps/mail/vendor/bytestream/horde-imap-client/lib/Horde/Imap/Client/Base.php - line 1404:

Horde_Imap_Client_Base->login("*** sensiti ... *")

/var/www/html/custom_apps/mail/lib/IMAP/FolderMapper.php - line 58:

Horde_Imap_Client_Base->listMailboxes("*", 5, [ true,true,true])

/var/www/html/custom_apps/mail/lib/Service/MailManager.php - line 546:

OCA\Mail\IMAP\FolderMapper->getFolders([ "OCA\\Mail\\Account"], [ "Horde_Ima ... e])

/var/www/html/custom_apps/mail/lib/Controller/AccountsController.php - line 474:

OCA\Mail\Service\MailManager->getQuota([ "OCA\\Mail\\Account"])

/var/www/html/lib/private/AppFramework/Http/Dispatcher.php - line 230:

OCA\Mail\Controller\AccountsController->getQuota(7)

/var/www/html/lib/private/AppFramework/Http/Dispatcher.php - line 137:

OC\AppFramework\Http\Dispatcher->executeController([ "OCA\\Mail ... "], "getQuota")

/var/www/html/lib/private/AppFramework/App.php - line 183:

OC\AppFramework\Http\Dispatcher->dispatch([ "OCA\\Mail ... "], "getQuota")

/var/www/html/lib/private/Route/Router.php - line 315:

OC\AppFramework\App::main("OCA\\Mail\\ ... r", "getQuota", [ "OC\\AppFr ... "], [ "7","mail.accounts.getQuota"])

/var/www/html/lib/base.php - line 1071:

OC\Route\Router->match("/apps/mail/ ... a")

/var/www/html/index.php - line 36:

OC::handleRequest()

The output of my config.php file in /path/to/nextcloud:

  'mail_smtpmode' => 'smtp',
  'mail_smtpsecure' => 'ssl',
  'mail_sendmailmode' => 'smtp',
  'mail_from_address' => 'notifications',
  'mail_domain' => 'mydomain.tld',
  'mail_smtphost' => 'smtp-relay.brevo.com',
  'mail_smtpport' => '587',
  'mail_smtpauth' => 1,
  'mail_smtpname' => 'myemail@gmail.com',
  'mail_smtppassword' => 'my brevo (sendinblue) smtp key',

I’m using Passbolt (self hosted password manager) and I’m using Brevo (sendinblue) as the mail server host, everything works fine but in Nextcloud it simply doesn’t work, I have no idea why. Please help me.

The Brevo config page tells, not to set encryption except on using port 465: