If your email account was hacked, the hacker will have stolen your contacts list. The hacker will not necessarily be sending emails from your email account to your contacts, he/she may "spoofing" your email address and then sending the emails from their own device to your contacts in an attempt to fool them into thinking it is you that is sending the email so therefore it must be a safe email.
Unfortunately even although you have changed your password, as the hacker will not be using your account to send the emails they will continue to be sent as the stolen contacts list can not be unstolen so will be still available to the hacker to use.
See link about "spoofing".
Email spoofing - Wikipedia
You should log onto your email account using a web browser, make sure you are using the desktop view and not the mobile view, and go to the settings that you will find by clicking on your user name at the top right hand side.
When in the settings go to "Mail" at the left hand column and then go to "Forwarding" and "Rules" and check if any forwarding or rules have been set up. If they have and if they were not set up by you you need to delete them
After doing that you will see a warning when ever you log on informing you that changes have been made. You can not turn that warning off but it will automatically stop flashing up in a few days.
You should also have a read through this link and carry out the advice it is giving.
How can I tell if my email account is no longer secure? | BT Help
