Today I would like to point out something that drove me crazy for over a week. A customer called us regarding some messages being generated from a server, let's call it SERVER1, and sent through smtp relay configured in Exchange, were being received with blank content (no email body). At first I though to myself... "Oh my god, here comes another end-user Outlook problem", but after I tried it myself, I saw that no matter what client you tried to open the message with, outlook, gmail, or any other web or installed client, all the emails sent from this server were completely blank.
I tested it myself with the following:
220 internal.relay.domain.com Microsoft ESMTP MAIL Service ready at Tue, 9 Jul 20
13 13:05:46 +0200
helo mydomain.com
250 internal.relay.docout.es Hello [172.28.0.35]
mail from: testemail@relay.com
rcpt to: destination@domain.com
250 2.1.5 Recipient OK
data
354 Start mail input; end with <CRLF>.<CRLF>
to: destination@domain.com
from: testemail@relay.com
subject: subject from SERVER1
This is my content
.
250 2.6.0 <5cf64727-f4bf-44ca-a084-e4e4d432964b@SERVER1.domain.com> [Internal
Id=3365140] Queued mail for delivery
quit
221 2.0.0 Service closing transmission channel
Sure enough, just as customer said, this mail was received with blank contents instead of the "this is my content" text.