Undelivered Mail Returned to Sender

More and more mail to the guests is not delivered. When I try a second or third time, finally it is delivered. Not only mail from our mailserver is undelivered, also from payment receipts from Stripe.

The message I get in return is: 530 5.7.0 Must issue a STARTTLS command first (in reply to MAIL FROM command)

BrookAve 2 years ago


Hi Arjen


This is not a BdC support issue, this is a "your mail server  issue".


Its a permission issue with you r mail server and where it connects to receive, such as a smart host or imap/smtp relay such as gmail.


TLS settings typically are on port 465 for inbound connection.


You should talk to who ever setup /looks after your mail server.


PS: you cant email guest after 7 days after check-out date.




Arjen van Berlo 2 years ago


I'm not talking about the TLS-command, but the STARTTLS-command. This command is used first when a mailserver tries to deliver mail to your mailserver. I'll send you the whole message, and your network administrator will know what I mean. I replaced the mailaddress with not-the-real-mailaddress:

This is the mail system at host ***.booking.com. I'm sorry to have to inform you that your message could not be delivered to one or more recipients. It's attached below. For further assistance, please send mail to postmaster. If you do so, please include this problem report. You can delete your own text from the attached returned message. The mail system <not-the-real-mailadress@guest.booking.com>: host ***.booking.com[***] said: *** Must issue a STARTTLS command first (in reply to MAIL FROM command)

BrookAve 2 years ago


Arjen you're not getting it,  you wont get support for this here.


and you cant email a guest who has left, more than 7 days.


You could try message BdC support about it but dont expectt much to happen, as they likely wont know what to do with it.


Kind Regards


Arjen van Berlo 2 years ago

Yes! I'm not getting it? Leave it then! But listen: - Messages from my mailserver AND from Stripe are not getting through

- It's about new customers who just booked

But I rest my case. Bye!

Kind regards!

Stefano Corsi 2 years ago

I agree with Arjen, we're sending messages through AWS SES and have the same problem, suddenly, since apparently the 25th of July, booking.com's mailer has started to complain about some STARTTLS.

It's a smtp issue, either the problem is with AMAZON AWS or with  intercommail.booking.com[]

I wouldn't exclude neither of those apriori.


John Mustard 2 years ago

I agree with Arjen and Stefano. Getting mail delivered to guests and received from guests using the booking.com messaging is quite a challenge. We need to be able to communicate efficiently and effectively with our guests, and routing mail through servers controlled by booking.com makes this task much more difficult than it needs to be.

BrookAve 2 years ago

How it really works....


  1. The booking system has an internal message system.
  2. Host logs on to extranet.
  3. Guest logs on to Booking Portal
  4. Host <> Guest message each other.
  5. Guest real email stored but hidden from Host using a automation API to create a temp mailbox on a linux mail server.
  6. Any attempt to use the displayed email address for guest results in a script pulling the messages from that mailbox and shown in the message view and vice versa.
  7. Notifications will email copies to host and guest.


The reason you wont have direct guest email is to prevent messaging outside of the BdC ecosystem. 


After 7 days post check out date, the system removes the temp mail box and blocks new messages to guest.

But if the guest initiates a new message to you then it is fine , and you can reply then.


Example:  why use booking.com and pay a commission if i can just deal with theguest directly ?? 

this is only  one reason they wont let you, and also gives them insight of message history if needed to refer to later for disputes on both sides.



Kind regards,

An IT veteran


PS: i'm not here to give IT support just advise you when i see it and sterr you in right direction, its up to you engage with the correct party or 3rd party service to resolve where needed such as paying an IT service to review your mailserver and provide once off support.