You could have, there are a few things that could affect this. First (and most obvious) is to make sure you have a data connection. Next, go to menu>settings>accounts & sync to make sure background data and auto sync are turned on, then select your yahoo account on the same page and look over the settings there. If that still doesn't solve it, open the app you use for your email and check the settings there. If none of this works, it could simply be that your phone is out of memory, but I would imagine you would have gotten a warning about that.
Thank you to the community members for assisting Robn. Robn, I would recommend to delete the e-mail account from the device and add it back. To delete the account, follow the instructions here: http://support.verizonwireless.com/clc/devices/knowledge_base.html?id=48067 . Let me know if you have any questions.
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I too had issues with the email app connecting to both yahoo and gmail ever since the 2.3.6 update. The instructions noted above were of no use on an LG Spectrum as restarting while pressing the home button did not bring up a special menu. What did work however, was to remove the yahoo email account. Go to the app, Get to the account settings and touchh the 'remove account' button. You may get a message about it removing all accounts. Do not worry, answer OK, That is how my Spectrum behaved and it deleted both my Yahoo and gmail accounts (Kept the Microsoft hotmail account which was the only one woorking). I then powered off the phone. Powered it back on. Went to the mail app. And went to add an account. I added back thhe yahoo account and then added back the gmail account. Both are working successfully now. Note that I had also installed Yahoo's email app which I used when the email app previously bacame flaky getting Yahoo mail.
Note that I hhad submitted ann email to customer support recently. TThey sent me back an email saying to install the Yahoo email app. I hope when the ICS update comes out, things will go smoother. Try what I did to fix my email app.