[Gmail-Users] Some emails that I sent didn't arrive

Hello.

I'm having some problems with gmail. Some of the emails I sent didn't
arrive. These emails appear in my gmail account like "sent", but I
think it isn't true because some people told me that they didn't
receive my messages.

I'm using web access, I'm not using any application to send emails.

Can anybody tell me what's happening? I'm having this problem since 3
months ago.

Thanks.