On-Prem Anonymous Relay - Current Solutions?

Brass Contributor

We've migrated to EXO, but like many large organizations with a lengthy on-prem history, we have a wide array of existing, mission-critical legacy solutions requiring **anonymous** SMTP relay support that cannot yet move to authenticated cloud relay. Over the next several years, these legacy solutions will be replaced, but for a period of time we need to keep a reliable anonymous SMTP relay solution on-prem.


We've been using a pair of virtual appliances (IMSVA's) for some time, and they've worked well but are costly (we send thousands of relayed messages daily from a wide range of on-prem apps/services).


Can anyone recommend a solid, fault-tolerant on-prem anonymous SMTP relay solution that works well with EXO?

2 Replies

Hi @SW-SoCo2 


did you tried IIS SMTP Relay i use it and it is very reliable and simple to configure with EXO.



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@Deleted Thanks for your reply. We've considered (but haven't yet tried) the basic IIS SMTP service; I was looking to see what else might be out there, in use and with solid performance. IIS SMTP may end up being the way we go, in order to take our heavy internal relay load off of Exchange Server itself, AND navigate the changes to Microsoft's EXO SMTP/relay services.