TLS connection slow

Hello Networking Wizards -

Any idea why internal connections to an SMTP server are quick, but external are slow? Or, how to start troubleshooting this type of challenge.

Here’s what I know. Internally, if I use the openssl s_client to setup a tls connection to the smtp server the “connect” occurs and then the TLS component establishes basically instantly. However, externally, the “connect” happens quickly but the TLS component takes about 3 seconds.

Any idea how to isolate where the problem is for this?

Thanks!