Why can't telnet connect? (for Centos)

Hi everybody. I'm investigating SMTP issues. Have any of you used centos and faced this issue before ? Yes, I know, I need to explain the problem, here are the details. I'm starting a telnet connection to an smtp server through my PC.

#telnet smtp.yandex.com 587
220 iva5-b9ce8295c822.qloud-c.yandex.net (Want to use Yandex.Mail for your domain? Visit http://pdd.yandex.ru) 1671766010-oQexA05YXKo1

Result successful server accessed and returned 220. But I am trying the same process on a server with centos operating system.

#telnet smtp.yandex.com 587
Trying 77.88.21.158...

The request remains on hold and does not proceed. Does anyone know the cause of this problem ? There are no restrictions due to firewall rules. I have full access to the firewall and no restrictions.

I am using postfix on my server. Do you think this problem could be caused by postfix? It doesn't connect to all SMTPs, not just this SMTP. It returns 220 on everything except the mail ports and it succeeds. It's really weird. Where am I missing ?