We have built an API that verifies a address existence in the respective MX using RCTP command. Their are many services available out there but we like to do it again since we have few clients who need this service, And we manage their lists.

The application uses more than just one way verification, from syntax to mailbox existence and spam databases. The application worked fine with all the ISPs like gmail, yahoo, msn etc but our test server's IP got blacklisted. Now we want to set-up a dedicated server and other things that will let up verify at lest 15-20k list per day.

So, my question is how to do it, What are the hardwares and softwares needed and any suggestion to make it more secure maybe using a advance SSL/TSL etc or using some relays, I dont know about it but got many suggestions about it. I am open for any architecture for the server and ready to spend any amount of money. In any situation the server's IP must not get BLACKLISTED.

This is not about capacity management because sending bulk request is not allowed without secure environment.

Thanks alot, Meeshal K


While you might have a valid reason to do mass verification of e-mail addresses such validations are also done in preparation of spamming these users and thus are often considered misuse - which will quickly get you onto blacklists. No TLS will help you in this case, because TLS only protects the transport but says nothing about abuse or not.

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  • your answer gave me direction to deal this issue, thanks a lot – Meeshal k Mar 5 '16 at 14:10

Simply put, there is no way to do this at a high volume that won't run against large email account providers' protection features and eventually get you blacklisted.

You are better off with different strategies to maintain proper lists, such as handling error codes correctly when delivering actual messages to remove invalid addresses from the list, using a confirmation loop when adding contacts to the list (double opt-in) and subscribing to / responding to feedback loop / list-unsubscribe requests automatically.

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    All good points and suggestions, but I might add that perhaps the best way of all is simply to outsource to bulk email services who do nothing but, and already have relationship with large mail providers and the blacklist maintainers themselves. – Xander Mar 4 '16 at 14:49
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    @Xander: I agree, however Meeshal K states that he's doing this on behalf of clients for whom he manages these lists. So it seems he's venturing into that business himself. – P_J Mar 4 '16 at 14:54
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    Ah, yes, good point. I didn't catch that on my first read. – Xander Mar 4 '16 at 14:57
  • Yes, you are right @Pascal Jolin and I have found some very remarkable points to consider from here and from paid professionals. Like IP rotation, DKIM etc. I am going to implement those according to my needs. i'll write about it on my blog and put a link here. And Thanks a lot for the answers really appreciated. – Meeshal k Mar 5 '16 at 14:09

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