What is the problem with SMTP?

Question

SMTP

Tell me how to defeat the problem, what could be the problem, through the roundcube / program it connects
via SMTP from the mailer - an error
Here is a transcript of the error message:
SMTP Error: Could not authenticate.
SMTP connect() failed. https://github.com/PHPMailer/PHPMailer/wiki/Troubl...
Connection: opening to a5-mail.ru:25, timeout=30, options=array ( 'ssl' => array ( 'verify_peer' => false, 'verify_peer_name' => false, 'allow_self_signed' => true, ),)
Connection: opened
SMTP -> get_lines(): $data is ""
SMTP -> get_lines(): $str is "220 a5-mail. ru ESMTP Exim 4.84_2 Mon, 26 Mar 2018 18:28:13 +0300"
SERVER -> CLIENT: 220 a5-mail.ru ESMTP Exim 4.84_2 Mon, 26 Mar 2018 18:28:13 +0300
CLIENT -> SERVER: EHLO b2bmails.ru
SMTP -> get_lines(): $str is "250-a5 -mail.ru Hello 33.ip-164-132-45.eu [164.132.45.33]"
SMTP -> get_lines(): $data is "250-a5-mail.ru Hello 33.ip-164-132-45 .eu [164.132.45.33]"
SMTP -> get_lines(): $str is "250-SIZE 52428800"
SMTP -> get_lines(): $data is "250-a5-mail.ru Hello 33.ip-164-132 -45.eu [164.132.45.33]250-SIZE 52428800"
SMTP -> get_lines(): $str is "250-8BITMIME"
SMTP -> get_lines(): $data is "250-a5-mail.ru Hello 33. ip-164-132-45.eu [164.132.45.33]250-SIZE 52428800250-8BITMIME"
SMTP -> get_lines():$str is "250-PIPELINING"
SMTP -> get_lines(): $data is "250-a5-mail.ru Hello 33.ip-164-132-45.eu [164.132.45.33]250-SIZE 52428800250-8BITMIME250-PIPELINING"
SMTP -> get_lines() : $str is "250-AUTH PLAIN LOGIN"
SMTP -> get_lines(): $data is "250-a5-mail.ru Hello 33.ip-164-132-45.eu [164.132.45.33]250-SIZE 52428800250 -8BITMIME250-PIPELINING250-AUTH PLAIN LOGIN"
SMTP -> get_lines(): $str is "250-STARTTLS"
SMTP -> get_lines(): $data is "250-a5-mail.ru Hello 33.ip-164-132 -45.eu [164.132.45.33]250-SIZE 52428800250-8BITMIME250-PIPELINING250-AUTH PLAIN LOGIN250-STARTTLS"
SMTP -> get_lines(): $str is "250 HELP"
SERVER -> CLIENT: 250-a5-mail.ru Hello 33.ip-164-132-45.eu [164.132.45.33]250-SIZE 52428800250-8BITMIME250-PIPELINING250-AUTH PLAIN LOGIN250-STARTTLS250 HELP
CLIENT -> SERVER: STARTTLS
SMTP -> get_lines(): $str is "220 TLS go ahead"
SERVER -> CLIENT: 220 TLS go ahead
SERVER -> CLIENT: 250-a5-mail.ru Hello 33.ip-164-132-45.eu [ 164.132.45.33]250-SIZE 52428800250-8BITMIME250-PIPELINING250-AUTH PLAIN LOGIN250 HELP CLIENT - >
SERVER: AUTH LOGIN
SMTP -> get_lines(): $str is "334 VXNlcm5hbWU6"
SERVER -> CLIENT: 334 VXNlcm5
c2FsZUBhNS1tYWlsLnJ1
SMTP -> get_lines(): $str is "334 UGFzc3dvcmQ6"
SERVER -> CLIENT:334 UGFzc3dvcmQ6
CLIENT -> SERVER: MjExMTIx0LXRiQ==
SMTP -> get_lines(): $str is "535 Incorrect authentication data"
SERVER -> CLIENT: 535 Incorrect authentication data
SMTP ERROR: Password command failed: 535 Incorrect authentication data
CLIENT -> SERVER: QUIT
SMTP -> get_lines(): $str is "221 a5-mail.ru closing connection"
SERVER -> CLIENT: 221 a5-mail.ru closing connection
Connection: closed

Answer 1

Everything is written there - Password command failed: 535 Incorrect authentication data