Blocking spam senders rarely works well because in decreasing spam as spam senders tend to change the addresses spam is sent from often as they got blocked at a higher level fairly quickly.
You've said it's a domain that you own, so a couple of things you can do because dealing with a whole domain is a bit different to dealing with a single address...
Firstly, make sure you are have not got your mail set as "catch all" so you are only collecting mail sent to specific addresses @ your domain... i.e. if your address is
[email protected] then you only want to be collecting mail addressed to
[email protected] and rejecting mail that is sent to any other
[email protected]. This may mean setting up several mailboxes with your mail provider and several matching account on your mail software.
I'd also make sure you are not using single word/name addresses at your domain because having a address like
[email protected] is going to attract lots more spam than an address like
[email protected].... similarly addresses like
[email protected] are more likely to receive spam than addresses like
[email protected].
The other thing for you to do is stop trying to block spam on your computer and try and block it at the server level, your current mail hosting provider may offer tools for this already, if not consider changing your provider to one that does offer effective spam filtering (any running something like spamassasin will be effective, also if any say they offer greylisting that is a very effective method)... have a look here under "Spam Filtered Hosted Email Services"..... I can't really recommend any of them as I have no experience of using them (I run our own servers and filtering where I work)
Finally.... you can probably set your mail software to auto empty your deleted items on exit to save you having to do it manually.