I am currently receiving a lot of inquiries about Exchange Server and sending emails via IONOS. As of January 15, 2024, IONOS will discontinue the smarthost function for IONOS mailboxes, which in turn means that Exchange servers can no longer use IONOS as a smarthost. Further information from IONOS can be found here:
Apparently there are quite a few people who are affected by this shutdown, so here is a short article on the subject.
Which configuration is affected?
All Exchange servers that use a send connctor with IONOS as smarthost are affected by the deactivation of the smarthost function. Here is an example of an affected configuration with smtp.ionos.de as smarthost:
Konkret bedeutet dies, dass Exchange keine Mails mehr an Empfänger im Internet schicken kann. Eigentlich ist diese Konfiguration auch schon recht veraltet. Früher hat man diese Art der Konfiguration häufiger angetroffen. Meistens wurden damals die E-Mails via POP3 und POP Connector (bspw. POPcon) aus einem Postfach beim Provider abgeholt und an einen on-Prem Exchange Server zugestellt. Der Versand von Mails via Exchange erfolgte dann über den Smarthost, bzw. den SMTP Server des Anbieters. Damals hat man dies gemacht, da nicht jeder eine feste IP hatte, der Himmel noch Wolkenlos (ohne Cloud) und Microsoft Small Business Server ziemlich angesagt war. Die Betonung liegt hier auf „war“.
What options are there?
First of all: Exchange servers have not supported sender-based routing for a long time. It is therefore not possible to adapt the Exchange configuration to use multiple mailboxes for sending mails. Although there are third-party tools (such as ExSBR) with which Sender Based Routing is possible, but this does not make the configuration any better. There are better options:
Option 1: Cloud AntiSpam provider
There are a large number of Cloud AntiSpam solutions and most of them are particularly suitable for smaller companies. Most of these solutions also include the very smarthost function that IONOS is now setting up. In principle, almost all Cloud AntiSpam solutions work according to the same principle: The MX record of a domain points to the Cloud AntiSpam provider. The provider filters out bad mails with its solution and sends the good mails to any mail server. As a rule, the on-prem Exchange server only needs to be accessible somehow, for example via DynDNS. As I said, there are a variety of providers for companies of all sizes and implementation is simple: just change the MX entry and send connector, which is often enough. As a bonus, you often get state-of-the-art spam filters.
I didn't want to mention any names at first, but I did mention ExSBR by name:
But I don't want to recommend anything, so don't share any other providers in the comments.
Option 2: Selber machen…
I'm not questioning on-prem Exchange Server, a company will have its reasons for having an on-prem Exchange Server and not migrating it to Office 365, for example. After all, it is quite expensive to operate an on-prem Exchange server, so you could also make it a little easier for yourself and no longer use the mail services from IONOS. In this case, of course, you need at least one fixed IP. You then have to take care of the AntiSpam issue yourself, here you could either use the rather rudimentary AntiSpam features of the Exchange server or use a special appliance / e-mail gateway or software. So here again there are many possibilities, but of course you have to take care of all the email-related issues yourself. If you don't want to do that, you could choose option 1.
So if you are looking for a special appliance or software to receive and send e-mails directly yourself (MX on your own IP), you will find it here:
Exchange itself already has everything you need to receive and send emails directly. IONOS as a smart host and POP3 mailboxes, as well as a POP connector, are not required. However, a fixed IP is a prerequisite here, but here too there are countless possibilities if you get a little creative.
Option 3: Exchange Hybrid
Anyone who has wondered whether the POP mailbox and smart host configuration in conjunction with an on-prem Exchange server will still make sense in 2023 and has already considered Office 365 could consider this option.
Exchange servers enable hybrid operation with Office 365. In hybrid mode, Office 365 can be used to receive and send emails (MX entry points to O365). The Exchange mailboxes do not necessarily have to be migrated to Office 365. In hybrid mode, Office 365 can take care of receiving/sending and the AntiSpam functions and deliver the mails to the on-prem mailboxes.
Personally, it's been a few days since I set up a fresh Office 365 tenant for Exchange Hybrid, but I seem to remember that no Office 365 licenses are required if the mailboxes are still stored on-prem and no Office 365 services are used. So it should be enough to synchronize the accounts via AAD Connect to EntraID and not assign a license. In hybrid mode, sending / receiving and routing to on-prem should then already work.
Glaub ich…. Kann das jemand bestätigen oder wiederlegen?
Option 4: There are other smart host providers
There are other providers who offer you a smarthost for sending emails. Most providers tend to come from the email marketing environment, but often offer standard email relay or smarthost functionality. For this option, it would therefore be sufficient to look for another provider and configure it as a smart host in the Exchange Send Connector. In this case, however, most providers charge according to the number of emails sent.
Here is another example:
Conclusion
If you are affected by the IONOS Smarthost shutdown and use an on-prem Exchange server, then my personal opinion is: Use option 1: Find a Cloud AntiSpam provider and also use this for sending emails. The configuration is usually simple and the providers provide support. The goal should be: No more POP accounts, you simply don't need them anymore!
Let's discuss this with pleasure.