Committed support for a complex SMTP issue

I have been having a problem with our ISP's SMTP server where from time to time emails would be bounced back with a "sender rejected" status. Naturally, I have contacted my ISP about this and they take steps to remedy the issue for it to only occur a few weeks later. In doing my own investigations (I originally believed the problem was that our IP address was on a blacklist due to spammers using the same ISP), I stumbled across a site that recommended that I speak with MailSoar's Pierre Pignault. He spent a lot of time looking at the issue with me and pointed me to a possible resolution yet to be tried. I have never before encountered anyone who was willing to spend so much time free of charge to help someone. This demonstrates the company's eagerness to help people resolve their issues. Thank you again, Pierre! I need to follow Pierre's recommendations before I can determine whether my problem will be resolved. But I know to whom I can turn if more assistance is required.