Security Risks- 'Allow tls' in ESMTP

[iteam]

HI,

I would like to have a session between azure O365 cloud and an on premise server behind Cisco ASA 5545. However the session cannot start due to STARTTLS failing. THe firewall cannot read TLS encrypted packets for port 25 hence the packets are dropped. A workaround for this is to 'allow tls' under ESMTP  in the configuration. However, since this change will be global, I would like to know the security risks associated with such a change. In case there is another solution kindly advise.

Thanks

[Ken Stieers]

Is theasy ESA the only box allowed to send/receive SMTP throught the firewall?

If so, no risk...