Emails are being rerouted to another domain

Some, but not all, mail intended for Domain A is being delivered to Domain B.  There is no technical relationship between the 2 domains.  Domain A's DNS has no reference to Domain B.  We're trying to find details about the DNS for Domain B, but we don't control it, so we're at the mercy of their admin.  Any ideas for what could cause this other than Domain B has some incorrect reference to Domain A?
Who is Participating?

[Product update] Infrastructure Analysis Tool is now available with Business Accounts.Learn More

I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

I'm not clear on what you mean.
Emails you send to domain A get routed to domainB
The only thing that would cause mail destined for Domain A to be delivered to Domain B would be an MX record for Domain A that points to Domain B.

Check your MX records for Domain A at
msCCareAuthor Commented:
Thanks.  I'm not the sender.  I'm Domain A.
Cloud as a Security Delivery Platform for MSSPs

Every Managed Security Service Provider (MSSP) needs a platform to deliver effective and efficient security-as-a-service to their customers. Scale, elasticity and profitability are a few of the many features that a Cloud platform offers. View our on-demand webinar to learn more!

If your dns has no reference to domain B then there is no way it should route over there.
-Domain B is your backup MX and for some reason your domainA server is not receiving mails
msCCareAuthor Commented:
that's about all we've been able to think of to rule out as well.  The only other wrinkle is that all the mail going to domain B seems to be routing through the same hosted email provider.  What are the odds that provider has a damaged record or something misconfigured on their end, so email that goes through them gets misdirected but email that goes through anybody else gets delivered as intended?
I would say it's unlikely, but possible.
If you are sure that this is the case and all your mx records check out then you shouldn't have a problem at your end.

However i'm curious on how you know the mails go to domainB?
is this also a company you know and they accept your mail or what?
msCCareAuthor Commented:
Exactly.  We know them a little and they called to say they were getting email that was addressed to us.  They were going to a general delivery mailbox, so they forwarded several messages over.  When we checked headers, we found that everything they had received had gone through this one provider.

It does seem unlikely.  Not sure why that provider would have different records from everywhere else in the world.  Can't think of anything else though.

It would make sense in case they messed something up in their own dns servers..
i would call the provider and ask them , then go further from there.
BTW companyB accepts mail sent to any domain?

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today

From novice to tech pro — start learning today.