postfix - can not send mail to gmail but receive

I configure a mail server using postfix and dovecot. Using this I can send and receive mail when it is local [ means, when mail is sending and receiving in myMailServer ]. Now problem is for others i.e gmail, yahoo etc. receiving from them is fine but sending is problem. I can understand why I can’t send mail to gmail or yahoo through myMailServer.

I’ll be grateful if any one help me. thank’s in advance.

here is my mail.log file data

Jul 1 05:55:09 mail dovecot: imap-login: Login: user=<bobby>, method=PLAIN, rip=202.79.21.235, lip=162.243.107.93, mpid=17429, TLS, session=<xQBa+482AADKTxXr> Jul 1 05:55:11 mail dovecot: imap-login: Login: user=<kisorniru>, method=PLAIN, rip=202.79.21.235, lip=162.243.107.93, mpid=17431, TLS, session=<dMJ7+482BQDKTxXr> Jul 1 05:55:39 mail postfix/submission/smtpd[17432]: connect from unknown[202.79.21.235] Jul 1 05:55:40 mail postfix/submission/smtpd[17432]: Anonymous TLS connection established from unknown[202.79.21.235]: TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits) Jul 1 05:55:42 mail postfix/submission/smtpd[17432]: 2EF8F123A44: client=unknown[202.79.21.235], sasl_method=PLAIN, sasl_username=kisorniru Jul 1 05:55:42 mail postfix/cleanup[17438]: 2EF8F123A44: message-id=72f3e760-50aa-e374-09d0-72c90cfe7bb1@livewellbd.com Jul 1 05:55:42 mail postfix/qmgr[17279]: 2EF8F123A44: from=kisorniru@livewellbd.com, size=711, nrcpt=1 (queue active) Jul 1 05:55:42 mail postfix/smtp[17439]: connect to gmail-smtp-in.l.google.com[2607:f8b0:400d:c07::1a]:25: Network is unreachable Jul 1 05:55:43 mail postfix/submission/smtpd[17432]: disconnect from unknown[202.79.21.235] Jul 1 05:55:45 mail dovecot: imap(kisorniru): Connection closed in=828 out=1777 Jul 1 05:55:54 mail dovecot: imap-login: Login: user=<kisorniru>, method=PLAIN, rip=202.79.21.235, lip=162.243.107.93, mpid=17441, TLS, session=<P6oN/o82CgDKTxXr> Jul 1 05:56:12 mail postfix/smtp[17439]: connect to gmail-smtp-in.l.google.com[173.194.204.26]:25: Connection timed out Jul 1 05:56:12 mail postfix/smtp[17439]: connect to alt1.gmail-smtp-in.l.google.com[2800:3f0:4003:c00::1b]:25: Network is unreachable