How to replace relay server with Sendgrid ..?

Question

We need to replace our Relay servers with Sendgrid on Azure . We cannot change the code in the applications. Applications send mails directly to on-prem SMTP relay server without any authentication , username or password. sender is also not an authorised .. ******@domainname.com but target email addresses are all valid.
now we want to replace this on-prem SMTP relay server and route all the emails to sendgrid directly.

sendgrid configuration requires username and password. we cannot change the code in the existing applications , these are COTS products . how can we configure sendgrid such that it will accept the request without username and password from specific hosts. is this possible ?

Answer 1

It does appear that SendGrid features SMTP relay, and this blog post is 101 on the feature itself. However, since SendGrid is a 3rd party offering, to gain better understanding of the offering it's best to contact them. From the point of Azure, you only set up the initial account on your subscription and charges are included with your subscription costs.