Email settings; MD5 Challenge Response

Question

Mostly out of curiosity....in the advanced settings for email, I had chosen 'password' as the method of authentication for both incoming and outgoing mail. Occasionally, when checking mail, it won't fetch anything, saying cannot retrieve mail for xxxx, password incorrect (or something like that) or it might say x number of messages unread. If I go back into advanced settings, the authentication method for incoming mail has defaulted to MD5 Challenge Response. After I change it back to 'password', I can successfully get my mail.
My questions are:
Is this setting just randomly changing itself? Or perhaps when I have reset/rebooted the iPhone, is it causing that setting to default to the MD5? And, what the heck is MD5 Challenge Response?
Thank you in advance.

Answer 1

It depends upon how Verizon has chosen to configure its servers, and I see no explicit indication at any Verizon site that it support CRAM-MD5 or any other form of authentication beyond plain text password authentication. You'll have to ask them to get a definitive answer.
In choosing a mail provider, it's best to find one which supports IMAP and not simply POP3, SSL connections for both IMAP and SMTP, and authentication. Major providers such as Comcast and Verizon typically fall down in this area. IMAP options are provided by Apple with .Mac Mail, AOL with AIM Mail or AOL Mail, and Google with Gmail. Notably missing: Yahoo and most of the options for mail via Microsoft.