I can not receive mail from other email address - error

[ThuHuyen]

Hello you!
I have used Imap to receive mail.
But I only send mail out, I can't receive mail from other email address.
I have checked MX record it's ok.
But when i access to ssh, and I typing line command:

telnet mydomain imap

I have got some information from my system:

trying My IP of server...
* OK [CAPABILITY IMAP4rev1 LITERAL+ SASL-IR LOGIN-REFERRALS ID ENABLE IDLE START TLS AUTH=PLAIN AUTH=LOGIN] Dovecot ready.
* BAD Error in IMAP command received by server.

* BAD Error in IMAP command received by server.

* BYE Too many invalid IMAP commands.
Connection closed by foreign host.

I think it's reason that I can't receive any mail from other email address.
What's happand here?
How can I fix it?
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I'm using CentOs7 and Roundcube