IMAP email issues

I have been using Comcast mail on my iPhone for 15 years I now have a 16 pro max.  I keep getting a pop up say my IP address is blacklisted and be sure I’ve entered in my correct password so my email will not come in although I can delete email and search..

i can get into mail online directly so I have verified my password works. Occasionally email comes in then stops again overnight. I went to Verizon that told me this was a common problem but had no support to offer me. 

Many years of information are in this account I need access to. Please explain what I can do. Using ports 993 and 587 that I have verified are correct online. Thank you so much!