Recently had a client delay receiving emails

A check of SMTP logs showed

4.7.0 SMTP; 403 4.7.0 TLS handshake failed

To investigate : 

Open Exchange Management Console

Go to Server Configuration and check Exchange Certificates check if there are any expired with SMTP next to them

Renew Self Signed Certificates  :

1. type Get-ExchangeCertificate to list the installed certificates

2. Match the certificate to the expired certificate (using subject the name and services) from the Console then copy the associated thumbprint

3. Type Get-ExchangeCertificate –Thumbprint INSERTTHUMBPRINTHERE | New-ExchangeCertificate

Renew Third Party Cert

1. Go through the process of Renewal with your Third Party SSL Authority

To disable Receiving email via TLS

Go to Hub Transport under Server Configuration, then Untick Transport Layer Security (TLS) for each Receiver Connector