I make some tests, like add my account to Gmail and i have these errors:
May 17 02:02:16 server1 postfix/smtpd[15270]: connect from mail-yw0-f174.google.com[209.85.161.174]
May 17 02:02:17 server1 postfix/smtpd[15270]: Anonymous TLS connection established from mail-yw0-f174.google.com[209.85.161.174]: TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)
May 17 02:02:17 server1 postfix/smtpd[15270]: warning: SASL authentication failure: Password verification failed
May 17 02:02:17 server1 postfix/smtpd[15270]: warning: mail-yw0-f174.google.com[209.85.161.174]: SASL PLAIN authentication failed: authentication failure
May 17 02:02:18 server1 postfix/smtpd[15270]: lost connection after AUTH from mail-yw0-f174.google.com[209.85.161.174]
May 17 02:02:18 server1 postfix/smtpd[15270]: disconnect from mail-yw0-f174.google.com[209.85.161.174]
May 17 02:02:32 server1 postfix/smtpd[15274]: connect from mail-yw0-f171.google.com[209.85.161.171]
May 17 02:02:32 server1 imapd: Connection, ip=[::1]
May 17 02:02:33 server1 postfix/smtpd[15274]: Anonymous TLS connection established from mail-yw0-f171.google.com[209.85.161.171]: TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)
May 17 02:02:33 server1 postfix/smtpd[15274]: warning: SASL authentication failure: Password verification failed
May 17 02:02:33 server1 postfix/smtpd[15274]: warning: mail-yw0-f171.google.com[209.85.161.171]: SASL PLAIN authentication failed: authentication failure
May 17 02:02:33 server1 postfix/smtpd[15274]: lost connection after AUTH from mail-yw0-f171.google.com[209.85.161.171]
May 17 02:02:33 server1 postfix/smtpd[15274]: disconnect from mail-yw0-f171.google.com[209.85.161.171]
May 17 02:02:43 server1 postfix/smtpd[15274]: connect from mail-yw0-f177.google.com[209.85.161.177]
May 17 02:02:43 server1 postfix/smtpd[15274]: Anonymous TLS connection established from mail-yw0-f177.google.com[209.85.161.177]: TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)
May 17 02:02:44 server1 postfix/smtpd[15274]: warning: SASL authentication failure: Password verification failed
May 17 02:02:44 server1 postfix/smtpd[15274]: warning: mail-yw0-f177.google.com[209.85.161.177]: SASL PLAIN authentication failed: authentication failure
May 17 02:02:44 server1 postfix/smtpd[15274]: lost connection after AUTH from mail-yw0-f177.google.com[209.85.161.177]
May 17 02:02:44 server1 postfix/smtpd[15274]: disconnect from mail-yw0-f177.google.com[209.85.161.177]
May 17 02:03:04 server1 imapd: Connection, ip=[::1]
May 17 02:03:11 server1 postfix/smtpd[15270]: connect from mail-yw0-f170.google.com[209.85.161.170]
May 17 02:03:11 server1 postfix/smtpd[15270]: lost connection after UNKNOWN from mail-yw0-f170.google.com[209.85.161.170]
May 17 02:03:11 server1 postfix/smtpd[15270]: disconnect from mail-yw0-f170.google.com[209.85.161.170]
May 17 02:03:32 server1 imapd: Connection, ip=[::1]
I have test the port 587 and TLS, with SSL and insecure connection.. same error all the times..
I don't know whats happen..