We have 5 email addresses on the same server. One of these email addresses suddenly started receiving spam messages. And I'm not talking about legitimate businesses sending out mailers. These are the disgusting and suggestive things that make you blush just reading the subject line. Then a second email address started receiving the same types of messages, easily around ten a day, if not more, each time from a different email address, so moving it to the junk folders and blocking the address doesn't make much of a difference.
I started realizing that my mails are not getting through to some of our recipients. Then the first email address that was spammed, got spam messages from itself. We checked with our service provider, and they said our domain was not hacked. However the spam did not stop and a third email address now started receiving it. We were concerned at our address being used to spam, afraid that it might go out to our address book, with our email address as the sender.
Then, my cousin found one of the emails I sent him in his junk folder, meaning our mails are now seen as spam.
Along with this issue, we also, around the same time, started having issues with our internet. It is connected to our wifi and then suddenly it would say "No internet connectivity". The connection lights on the router will flash for a while, sometimes even going red, and then reconnect.
Our data also spiked, using more than double what we usually do.
All this has been taking place in a period of about 2 weeks, maybe even 1 week.
We have Bitdefender installed on our computers and have run all the scans available on it. I've installed MalwareBytes and run a scan, but it found nothing noteworthy. I've tried to check startups, but am inexperienced in this regard, resulting in me looking at a list of programs but having no idea which ones are essential, which ones are harmful etc.
To me it feels like it all started with the spam emails and it's spiraling out of control. Any ideas of what I can do to fix it?