First, change the password on your email address. something "strong"...use capital and lowercase letters and numbers (XxX123ZzZ)
It sounds like someone signed up for a website/service that sends advertisements to your email address. The advertisements probably have the name of the site sending them. You might be able to go to that site and discontinue your account there.
You can also block future advertisements using filters (assuming all the advertisements have something in common...who sent it, subject, etc)
In the upper-right corner of your Yahoo! Mail page,
click the Options
link, then select Mail
from the menu.
On the left side of the page, click the Filters
On the top of the Filters
click the Add Filter
A page appears where you can define the rule and
the destination for the new filter.
Type a unique name for the new filter in the Filter
box, such as "advertisements"
Define one or more rules for the filter.
- From header-Who sent the message.
- To/CC header-Who the message is addressed to.
- Subject-The subject text.
- Body-The message or body text.
From the Move to Folder
list, choose the destination folder where you want the message to go (probably SPAM)
- Contains-the area must contain the
target text. For example, the target text "Chris" would match all
the following: "School project on Christopher Columbus,"
"I forgot to call Chris," "firstname.lastname@example.org."
- Does not contain-the area must not contain the target
text. (This is a negative condition.) For example, the target text
"Chris" would match any area that does not contain "Chris."
- Begins with-the area must contain the target text at
the beginning. For example, the target string "Chris" would match
"email@example.com," but not "School project on Christopher Columbus"
or "I forgot to call Chris."
- Ends with-the area must contain the target text at the
end. For example, the target string "Chris" would match "I forgot
to call Chris," but not "firstname.lastname@example.org" or "School
project on Christopher Columbus."
Click the Save Changes
to save the filter.
In the worst case you can just get a new email address and tell your contacts about it.