I'm going crazy with Yahoo and sending emails from an mail client with MailKit which manage tons of email but I'm cannot send to Yahoo only.
I tried to follow not only the MailKit documentation (https://github.com/jstedfast/MailKit/blob/master/FAQ.md#SslHandshakeException) but also the several posts found by googling which definitely advise me not to use the MX record of yahoo but to use authentication for third party apps and using a fixed params as mailserver, port and TLS
Despite this, I cannot deliver emails to valid yahoo addresses, and the behavior is very bizarre: if I connect without authentication, yahoo tells me "554 Email rejected", but if I connect with yahoo authentication it tells me "550 Request failed; Mailbox unavailable "when I receive tons of emails on the same email every day...I'm going to cry...
Here is the code and Yahoo's answer is there any good man to help me? Thank you so much in advance for your help, I have a very big problem with a customer.
Here the code used and the answers
WITH AUTHENTICATION
client.ServerCertificateValidationCallback = Function(s, c, h, e) True
client.CheckCertificateRevocation = False
client.Connect("smtp.mail.yahoo.com", 587, MailKit.Security.SecureSocketOptions.StartTls)
client.Authenticate(username, password)
Connected to smtp://smtp.mail.yahoo.com:587/?starttls=always
220 smtp.mail.yahoo.com ESMTP ready
EHLO mailsystem.xxxxx.xx
250-kubenode509.mail-prod1.omega.ir2.yahoo.com Hello mailsystem.xxxxx.xx [xxx.xxx.xxx.xxx])
250-PIPELINING
250-ENHANCEDSTATUSCODES
250-8BITMIME
250-SIZE 41697280
250 STARTTLS
STARTTLS
220 2.0.0 Ready to start TLS
EHLO mailsystem.xxxxx.xx
250-kubenode509.mail-prod1.omega.ir2.yahoo.com Hello mailsystem.xxxxx.xx [xxx.xxx.xxx.xxx]])
250-PIPELINING
250-ENHANCEDSTATUSCODES
250-8BITMIME
250-SIZE 41697280
250 AUTH PLAIN LOGIN XOAUTH2 OAUTHBEARER
AUTH PLAIN ********
235 2.7.0 Authentication successful
MAIL FROM:<no-reply@xxxxx.xx> SIZE=4892
RCPT TO:<xxxxxxxxxxxxxxx@yahoo.com>
550 Request failed; Mailbox unavailable
503 5.5.0 Need MAIL before RCPT
RSET
250 2.0.0 OK
WITHOUT AUTHENTICATION
client.ServerCertificateValidationCallback = Function(s, c, h, e) True
client.CheckCertificateRevocation = False
client.Connect("smtp.mail.yahoo.com", 587, MailKit.Security.SecureSocketOptions.StartTls)
Connected to smtp://smtp.mail.yahoo.com:587/?starttls=always
S: 220 smtp.mail.yahoo.com ESMTP ready
C: EHLO mailsystem.xxxxx.xx
S: 250-kubenode503.mail-prod1.omega.ir2.yahoo.com Hello mailsystem.xxxxx.xx [xxx.xxx.xxx.xxx]])
S: 250-PIPELINING
S: 250-ENHANCEDSTATUSCODES
S: 250-8BITMIME
S: 250-SIZE 41697280
S: 250 STARTTLS
C: STARTTLS
S: 220 2.0.0 Ready to start TLS
C: EHLO mailsystem.xxxxx.xx
S: 250-kubenode503.mail-prod1.omega.ir2.yahoo.com Hello mailsystem.xxxxx.xx [xxx.xxx.xxx.xxx]])
S: 250-PIPELINING
S: 250-ENHANCEDSTATUSCODES
S: 250-8BITMIME
S: 250-SIZE 41697280
S: 250 AUTH PLAIN LOGIN XOAUTH2 OAUTHBEARER
C: MAIL FROM:<no-reply@xxxxx.xx> SIZE=4892
C: RCPT TO:<xxxxxxxxxxxxxxx@yahoo.com>
S: 554 Email rejected
S: 503 5.5.0 Need MAIL before RCPT
C: RSET
S: 250 2.0.0 OK