E-Mails via custom SMTP are not being sent (Cloud beta)

I did register webspace, domain and email hosting with united domains. In Cloud console i can successfully setup the smtp server for my imap account / smtps server from united domains. On updating the settings in cloud console, i get the green success window indicating that the smtp configuration is updated successfully.

But no E-Mails are being sent / received.

TL;DR

The user is experiencing issues with sending emails via custom SMTP in Cloud beta. They mentioned that there was a typo in the username and that using another SMTP account from the same provider worked. They also found "Could not authenticate" error logs. The user has checked for spam but found nothing. They cannot see any logs from their mail provider. They are calling a web API to create email verifications, which works fine without custom SMTP enabled. The user has set up the SMTP server in the Cloud console successfully but no emails are being sent or received. There is no solution provided in the thread.

what are you doing to test sending an email?

i call web api like:

account.createVerification('https://captchores.de/verify-email').then(value1 => { console.log('Token: ', value1); },reason => { console.log('sendEMailVerificationFailed: ', reason); });

which works fine if i disable custom smtp config. if i re enable it - no mail gets sent. if disabled, i get the e-mail by appwrite mail domain.

have you checked your spam folder? Is there anything you can check on your provider side?

Yes, i hav checked for spam. Nothing there. sadly no, i cannot check / see anything from mail provider. it only offers an webmailer - but nothing can be seen there.