Email security settings

Well I did not get the notification e-mail from Cox so I assume my settings must have been okay but on Jan 25 I started having issues sending e-mails to groups like with 17 people.  I can send to an individual but not to groups.  I even tried putting three or four addressees and it still fails.  I use Thunderbird on my Windows 10 laptop but I am also having the same issue on my Apple iPad Air using the Apple Mail so I know it is not the e-mail apps I am using.  On Thursday I contacted Cox via the online chat and the conclusion was they have a mail server down and should be fixed within 24 to 72 hours but it would still be up to me to check to see if it is fixed.  I think since so many people are having this issue I would think for good customer service they would collect the e-mail addresses of all having the issue so they can send out a message to say the issue is fixed.  They might get the mail server fixed but we might still be having the issue.  I hope they are reading this and feel it might be a good idea to get back to the people having the issue instead of letting us just guess they have it fixed.  I had another talk with Cox again this morning because I still have the problem and he still tells me they are still having issues with the mail server so my question to him was well why am I still able to send e-mail to a single user.  He says it is working with limited abilities.  I worked in IT and Telecomminications for at least 35 years and if we brought up a new system and we had customers complaining of lack of service we would bring the old system back up if we could not fix the issue on the new system within 3 to 5 hours as the customers come first.  I worked for a financial services and we would have lost a lot of customers if we would tell the it should be fixed in 24 to 72 hours and with no notification as to when it is fixed.  The Cox rep suggested I use Web Mail which don't have the features I use and I have over 500 people in my address book that I don't have on web mail.  Needless to say I am pretty upset right now and even though I don't care much for CenturyLink I might have to consider them again.  My monthly Cox bill is over 330.00 a month so you would think you would get some better answers.  Since I did not get this notification that they sent out which means my settings musth have been right I would say my problem is not associated with this mail server outage.  And I don't think it is my equipment or software issue because I am using Windows and Apple iOS and they are doing the same thing.  The more I think about this I might go to the CenturyLink site and see what they have to offer.