verify email address?
Hi there,
Our company provides opt-in email marketing software, which is specialized in sending emails to a group of opt-in recipients. We have a strict anti-spam policy that prohibits the use of our email marketing software to send spam.
We find that there is a number of non-existent email addresses in our customers’ mailing lists. Apparently, it will damage our sending IP addresses’ reputation if we send emails to non-existent email addresses. So we decide to develop a procedure to verify whether the email address is existent or not. With this procedure, we will know whether the email address is existent or not before we send emails to these email addresses.
Now, can you tell me does such kind of procedure will damage our sending IPs reputation as well?
Your early reply is much appreciated.
Thanks,
Ellen

You can use excellent free email checker below:
http://www.ip-address.org/verify/email-checker.php
http://www.ipaddresslocation.org/email_lookup/check-email.php
http://www.find-ip-address.org/email-lookup.php
They are very trustful but can test only one email.
Hope this helps!