Is there a fully EOP functionallity at SMTP-relay and how are the limits?

Copper Contributor

Hi Everybody,


we are considering to use the SMTP-functionality of ExO to drive mails additionally from a local server. The SMTP relay is described as one of three solutions on this site:


How to set up a multifunction device or application to send emails using Microsoft 365 or Office 365...


These three solutions are possible:

- SMTP client submission

- Direct send

- SMTP relay


SMTP relay seems to be the unrecommended solution of these three, but it is useful in some cases. In one row is the hint, that there is no possibility to bypass the antispam functionality. The question is here: Is this a fully activated EOP? I ask because normally you have to license the standalone version of EOP for on prem environments (it's not really a cheap service). And for the the SMTP relay solution there is no ExO License needed, which always would include the EOP.


Is this EOP for free? Or what else is it? It is not clear described.


Another question is regarding the limits. In the linked site you can find regarding this "Reasonable limits are imposed." Does anyone has further information about it? It is also not described and some people say, there is no limit, some other say the limits will come soon (1st of January 2025). I really don't want to take advantage of this system but i need to know the facts about it.


Thanks for any contribution!

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