I am wondering when I want to filter emails with subject “viagra” and delete them, gmail doesn’t allow to set a filter with “viagra”. why? I have serious doubt gmail actually promotes viagra spams!
I don’t have a gmail account so I don’t know. Have you ever gotten a viagra email? Maybe it’s already filtered so you can’t create what would be a duplicate filter?
I didn’t have any issues with creating a filter for Viagra, viagra just now. 
I tried it in different days, and I can’t create a filter for viagra. and no, I don’t have a duplicate filter for that.
Just report it spam 2-3 times .After that u will not get mails regarding that.
Start marking the emails you do not want to receive as spam. I’m certain in some time google will mark them as spam automatically
I have gmail and it is one of the best email packages I’ve used for keeping spam out of my inbox, without any filters.
Gmail is the best product I have found for keeping emails out of your inbox. It greatly speeds up your processing of emails when it sends everything to the junk folder.
Just say them you think that is spam and I’m sure since that moment all unwanted emails will be in the spam folder of you
To filter spam mail, use another word which can identify that email.
Once that added to the spam manually all next emails with similar structure will be there for sure
Placing all the wanted emails in the spam folder along with the unwanted ones is not useful.
I do it once on google apps mail and it never shows in my inbox again. Even if you are correct , still better than any other email service.
In my opinion G mail is not a spammer. It allows to filter unwanted mails. It is the best mailing system that available now. The mails that are spam directed towards the spam section.
I don’t know if this is right. Just new in using gmail.
You can start by setting up spam_filters for certain messages TO, CC, From, etc…message headers to avoid most of spammer mass mailing dictionary trix; as well as checking the Report_Spam Box before deleting the messages to help the Googler Team with thier research on these INet menaces. You can also have your Gmail spam folder dump at set intervals. See; Help + Settings.
Where are you trying to set that keyword for a filter settings? May be you should try only putting that keyword in message option, TO And Form option won’t allow you to put a word without @.
Gmail is pretty good for spotting spam in my experience. My spam folder is almost scary to see :).
Gmail has the best spam filter imho. I have used gmail for more than 4 years and I hardly need to delete or report a spam email. In comparison, I receive spam emails in my yahoo inbox almost everyday.