Per Allen1 and Herd1 the solution below does work ...
on the iphone 8, my friend's verizon email started to do/have the same trouble, giving an error message when sending email (sorry I don't have the exact error any more).
In the settings for the verizon account, scroll down to the Outgoing Mail Server, click to open SMTP, remove the Primary Server (which probably says verizon.net), below you should see the smtp.aol.com option, click it, enable it, use the @verizon.net for the username and use port 465. WHEW!!!! Shame on Verizon and/or AOL for not sharing this info with folks. But, a lot of us know ... it is likely a way to get everyone to change to IMAP (which I bet they'd prefer).
To send outgoing Verizon email, now hosted on the AOL email servers, your email client or app must support *** OAuth 2.0 Token *** outgoing mail server authentication. If your client does not support this then you can only use web email to send emails. Thank you for wasting my time (please note sarcasm) large bureaucratic Verizon AOL for NOT PUBLISHING THIS ANYWHERE.
I tried the following experiment to verify that Verizon outgoing email server required OAuth 2.0 Token *** outgoing mail server authentication. For the Apple iOS Mail client on iPhone or iPad using iOS 10.x, I was UNABLE to send email to my Verizon email account, now hosted and converted to AOL email servers. I used smtp.aol.com as the host name for the outgoing email server, along with trying both port 465 and 587, both using Verizon DSL (Wifi On) and direct to my cell carrier (Wifi off) on my iPhone. I event deleted the account on the Apple Mail client and re-set it up using the builtin Apple Mail client set up utility for AOL which sets up my verizon.net (full email account name with verizon.net included) as an imap account. None of these worked.
I then set up the account on an iPad with iOS 12.1.4 and I again used the the builtin Apple Mail client set up utility for AOL which sets up my verizon.net (full email account name with verizon.net included) as an imap account. This time it worked easily. I could easily send emails. The only difference is that the APPLE iOS Mail client App for iOS 12.x supports *** OAuth 2.0 Token *** outgoing mail server authentication. [ioS 10.x does not and I am not sure if iOS 11.x does support this or not, though there is some articles that do suggest that the Apple Mail client does support OAuth 2.0 Token outgoing mail server authentication in iOS 11.x]
Also it is interesting to note that certain MS Exchange server versions now also require OAuth 2.0 Token outgoing mail server authentication support as well.
So the simplest solution to get your Apple iOS email client to send email using a AOL hosted verizon.net outgoing email server, is to upgrade to iOS 12.x or later on your ipad or iphone.
And once again, the issue is not Apple support of OAuth 2.0 Token outgoing mail server authentication, but rather the AOL-Verizon support organization in not notifying their end users about the requirement to use this to send outgoing emails starting back in 2018. This is just another one of the reasons that I have migrated away from using my verizon.net account except in rare situations. AOL-Verizon is simply unreliable.
And to AOL-Verizon Support management - Thank you for wasting my time (please note sarcasm) large bureaucratic Verizon AOL for NOT PUBLISHING THIS ANYWHERE.