An important email got hacked (I got a notification from my provider that he changed the PW because my email login was used worldwide to send out emails, mostly spam I guess). I assume it was hijacked and not spoofed.
This email is usually used to register web services etc. for example it is used with AWS3, heroku etc. I have no clue how someone got access but now I am here, shit happens.
I need to figure out what happened exactly, but I dont know where to start.
I contacted my provider, so I get detailed numbers on how many emails were sent out and I will also change every password and use simple antivirus, but I am afraid that this is not enough?
I also checked every email which I received in the last weeks, there was nothing suspicious.
Thank you all for the answers, they still help me to be prepared in future.
According to the current situation:
My provider answered very fast and it seems that the issue was caused by me. I use this email to send out news to our users and every week we have more users and obviously more emails. The automatic notification and PW reset was triggered by me sending out those emails. I simply have to adjust security level of this email and thats it.