Hello,
Rebex Secure Mail is a product which has been continually developed by in-house Rebex.NET programmers since 2006.
Rebex products, including IMAP, are trusted by thousands of organizations/developers worldwide.
From the amount of support requests related to Rebex IMAP that we receive I think I can say that IMAP class is stable, mature and reliable.
The full version of the component comes automatically with a 1 year support contract which means that you get priority email support (email questions answered within 1 business day) as well as access to hotfixes, and all new versions released within the support contract validity.
So in case you run into some trouble with the Rebex IMAP (part of Rebex Secure Mail), then you write us email to support@rebex.net and we'll get back to you within one business day. We usually fix issues found by our clients within a very short time or at least provide a workaround quickly to solve the issue.
If you are interested in seeing references, then some of our Secure Mail customers (and they're names and companies are real so you can check with them personally :-) were kind enough to share their words of praise.
You could also check a general forum, like stackoverflow, there you will also see that people are using Rebex components and from what I have seen they especially appreciate the support and hotfix delivery times.
You could also check the questions related to IMAP and our support times and replies at
http://forum.rebex.net/tag/imap
If you decide for Rebex, here is a link to purchase Rebex Secure Mail component.