Something strange has happened regarding my email account.

[loosethepounds]

For reasons that are not important I had to go to a foreign embassy for a number to complete my business.
The email address I used was [email protected] business account.

Today on my personal account [email protected] I received the number I needed.
They are not connected. The embassy has not been given my personal email

Am I missing something.

It's not clear if you sent them a message from your business account and they replied to your personal account? If so, is your personal email listed anywhere on your email footer?
Or did you tell them your business email verbally and they wrote it down? If that happened, are you certain you definitely gave them the business one?

Does anyone at the embassy know you (if they lost your email then did someone say, oh not to worry, I have her email address somewhere).

If none of the above, then are you suggesting they stalked you to discover your personal email, then used it so that you would know they had stalked you? Does your purpose for visiting them make this likely? Ie would they gain anything by doing a background search on you, or was your visit completely innocuous (like you are a florist delivering flowers)?

@SmokeySmokeyBaconthe paperwork I handed in had my business email on it.
I don't know anyone at the embassy. Anything to do with the business has that email.

My personal email is not known at work.

Have you ever applied for a visa to go on holiday? Or immigration matters for yourself? Married someone with an immigration history? A lot of the Gov systems are linked so providing your email for something else could mean they have it on the system.

@loosethepounds in that case they've found out your personal email by other means. Not difficult I imagine, but the question is a) why would they want to, and b) why would they want you to know that they had done it?
Since you aren't sharing what your business relationship with the embassy is, then only you can guess the answers to these.

OP said it was a foreign embassy, so I assumed it was not her own government or the embassy of her birth country or similar. eg she is completely British and she was visiting the Turkish embassy for work.

It’s easy for those with the right technology to do (and I’d certainly assume embassies do) so I suppose it depends on whether the nature of your reason for requesting the information would give them reason to do the searches and make the connection, then reply to your request using the wrong email in error..

That’s happened to me with gmail and live (formerly Hotmail) . Technological convergence!

I need an NIE number from this embassy to sell a property.

I was born in the UK.

So did you purchase this property? Or did someone else purchase it and you are selling on their behalf? If you purchased it they could have your email from then? Or if you are selling it on someone’s behalf have they provided the embassy with your email?

Have you previously been in contact with the embassy?

Could it be that they have your details on file from before?

My guess would be that the number you need is linked to information they hold on you already, so when they accessed that information they used the contact details already on file.

This property was purchased by someone who is now dead.
I had no dealings with buying it. This is the first time I have had contact with the embassy.

Okay.
So you don't know how they got your email address, but you have no reason to suspect them of anything sinister.

It's impossible for us to guess how they got it, since we don't know all the details of your dealings with them.
I suggest you just ask them if you are curious.