We've been using Evo email for years with no problems.
 
Yesterday we discovered that one of our customers had not been getting emails for a couple months. There were no error messages from Evo, or bounce messages from the server. I discovered it trying to send an email from my web client - I then got a "Delivery Status Notification" of an abort after 1 seconds. Long story short is, I discovered that his mail server decided it didn't like short From email addresses. So I changed to a longer one that it would accept (using my webmail client, not Evo).  
 
I also updated the other computers that had a short email address, and they seem to be working ok.
 
However, I was having problems sending from my computer. I would get the "Email NOT sent" message. The really strange thing was that I could send to anyone at my domain, but no one else.
 
I finally discovered the problem. In the interim I had tried using my gmail account (it didn't work - I guess because they require a minimum of SSL?), and when I changed back, I put in the address as smpt.domain.ext, not smptout.domain.ext...
 
So, if you have customers not getting emails, it may be that their server is rejecting them because your address is too short. And make sure you use the proper SMTP address!
 

Well I spoke too soon.
 
For some reason, I have been able to send from Outlook, but not from Evo (customer just doesn't get it) or Webmail (I get a "Delivery Status Notification" of abort status).
 
I even created a new legacy email address - sales at vermonthardwoods dot com, same issue: cannot send from webmail. Seems to be that their mail server doesn't like Godaddy.
 
Just in case it was a fluke, I tried again from Outlook, and the customer received it. I triple checked the settings and Evo and Outlook are using the same SMTP server, username and email address. I even have both set to Reply To the same (different) address.
 
What in the world??
 
This is real instigation to update to the latest version so I can use a Gmail address. It's either that or get an email account with our local internet provider and HOPE that works...