Charter email no longer sends on cellular data

I've had the same Charter email address for 10+ years and also have had this iPhone 13 Pro for several years with Charter email working. I noticed a few weeks ago that Charter will not send email when on cellular data...they just sit in the Outbox until I get home on my Charter wifi. It appears, also, that Charter email will ONLY send when on a Charter wifi...so public places that are not using Charter as their ISP fail to send. I believe it worked fine up until recently, however, I cannot be 100% sure because I really don't send that many emails a)from my iPhone and b)when I'm not at home. During this time I assumed that maybe Charter didn't want users sending email unless on the Charter network for some kind of anti-spam/security belief. But after more thought that doesn't sound right AND there would be some mention of it on the Charter website or Google.

I have googled extensively and cannot find anyone reporting this exact problem. I refuse to call Charter because they are clueless. I've checked their website and all is correct. Additionally, I have not changed any email settings on my iPhone since setting it up when I bought the iPhone a few years ago.

My SMTP settings are:

Host name: mobile.charter.net

User name: <my email address@charter.net>

Password: <my password>

Use SSL: Enabled

Authentication: Password

Server Port: 587

iOS is 17.3.1 and I believe I updated to that a few months ago. I guess the iOS flavor could have something to do with this or it could simply be a coincidence.

Any ideas?

Thanks!

[Edited by Moderator]