Unfortunately due to the limited availability of IP addresses sometimes they are re-used from sources that have been black listed in the past. Generally blacklists are updated within 30 days of an IP not being reported for spam.
However many services like Microsoft, Google, Yahoo and others, have taken to using their own systems and IPs will remain blocked until specifically requested that it be removed.

This is a list of resources for ensuring your emails are received by these major providers.

http://bulkemailguidelines.blogspot.com/p/gmail-yahoo-hotmail-and-aol-bulk-email.html

+++++++++++++Microsoft email services+++++++++++++++++++++++
https://support.live.com/eform.aspx?productKey=edfsmsbl3&ct=eformts&scrx=1

1. Contact Name:

2. What domain(s) are you sending to?

hotmail.com
live.com
msn.com
outlook.com
other

3. a: Contact e-mail address (this email must be valid to receive the investigation report):

b: What domain are you sending from?

4. How would you describe your company?

E-mail Service Provider (ESP)
E-mail Marketing Firm
University IT
Business (non-marketing)
Social Network
Consumer Marketing
Other

5. Outbound IP(s) or range(s):

Provide no more than 256 total IP addresses using any of the following formats:
– Ranges should be entered in CIDR format:
Example: xxx.xxx.xxx.xxx/24
– Use a semi colon to separate individual IPs or IP ranges:
Example: xxx.xxx.xxx.xxx; yyy.yyy.yyy.yyy
Example: xxx.xxx.xxx.xxx/28; yyy.yyy.yyy.yyyy/28

Copy and paste any error messages:

Provide the URL of your web site:

==============Verizon=================

Verizon Blacklist – http://my.verizon.com/micro/whitelist/RequestForm.aspx?id=isp

================Cox===================
Cox – http://postmaster.cox.net/confluence/display/postmaster/Error+Codes
McCafee –

==============mxlogic=================

Reference
https://portal.my-tss.com/knowledgebase/130/Comcast-is-blocking-an-IP-number-as-SPAM.html

Ticket #29963526 – ticket 29916866 IP’s received were/are blacklisted

=================AOL==================

https://postmaster.aol.com/whitelist-request#contact-info

https://postmaster.aol.com/whitelist-request

================gmail=================

https://support.google.com/mail/answer/188131
https://postmaster.google.com/managedomains?pli=1

================Comcast================

http://postmaster.comcast.net/block-removal-request.html

http://postmaster.comcast.net/feedback-loop.html

+++++++++++++Bulk Mail Guidelines+++++++++++++
Google
https://support.google.com/mail/answer/81126?hl=en

Yahoo
https://help.yahoo.com/kb/SLN3435.html