I have forgotten or I forgot

[kalhori]

Dear Sir/Madam,

I sent an email to someone and there were some questions about a software in my email. when I sent the email I knew I forget to ask him a question.

I want to send a new email to him to ask my question. which sentences is the best? actually I'm confusing in present perfect tense now.

Dear X,

I have forgotten to ask you this question.
put my question here.....

or

Dear X,

I forgot to ask you this questions.
put my question here.....

Best Regards,

 

[MikeNewYork]

I would say "I forgot to ask you this question in my previous e-mail."