Encrypted Mails

Hi All, (sorry for the english)

I have some troubles with a new flow I have to design.

For the moment, I have 1 mail flow going in webMethods.
The mails are signed and encrypted by the sender and I have its certificate and private key to decrypt the mail and get the attachment.

I need to receive mails from different senders to a single adress which is my entry point.

But I don’t know how decrypt the mails with only one certificate and 1 private key.

Is it possible to receive signed/encrypted mails from different senders to a single mail adress ?

Do the senders need my certificate/key to signed and encrypted mails ?

Thanks in advance