I think several of mails are classified as spam.But Gmail and other Public Email providers has no issues. It might be a false positive cases with the associated tools
Is there a tool or a way by which i can verify this.
The only surefire way to see if an email is classified as spam is to... send it, and see how it shows up on the other side. Any email server can classify any incoming email as "spam" or "not spam" or "slightly spammish" or whatever based on any arbitrary criteria, which may include email source, contents, or the phase of the Moon or the degree of incompetence of the intern who last played with the server configuration. In any case, such rules are local, often change without notice, and are almost never advertised in any way. Antispam rules are a heuristic hide-and-seek game with spammers, and secrecy is crucial (this is security through obscurity, because there is nothing better available).
When I send an email to a recipient on Hotmail, the Hotmail server classifies my email as "spam"... because my name contains a "forbidden word". No sysadmin at Hotmail admitted as such, but I made extensive tests (implying sending many emails from my own server, with various characteristics, and using an Hotmail account to see them) and I am fairly sure that I pinpointed the reason (if I send two completely identical emails, except for the sender name, being "Thomas Pornin" in the first and "Thomas Portin" in the second, then only the former is marked as "spam").
In order for a mail to be classified as spam it has to fail a multitude of tests maybe your mails have specific words in the title or the senders address is way to weird or the header is getting corrupted in a certain way or and maybe that's your problem: many people are custom filtering your emails as junk/spam.
if you can edit your question to include an example someone might be able to provide you with some more definite answer.
Generally the best way is to ask your friends if they received the mail or notify your readers that the email might go to spam-folder so they will have to mark it as normal mail.