Yandex email setup other SMTP

Hi,

I authenticate SMTP via Yandex Mail service. Test email works fine and receiving. Once I receive the test mail, I can see an error as below.

EMAIL DELIVERY ERROR: the plugin WP Mail SMTP v2.6.0 logged this error during the last time it tried to send an email:

Mailer: Other SMTP
SMTP Error: data not accepted.
Consider running an email test after fixing it.

Whether I received the test email, I can rarely submit a form. Most of the time I can’t submit the email at least. Most of the time I am getting this error.

There was an error trying to send your message. Please try again later.

I am using Contact Form 7 for forms.

Expect your prompt support on this.

Thanks in advance