mail says sender address is invalid

So when setting the outgoing mail server. In the “username” “password” optional feild, put in your email and password relatively.

I think the servers get confused because you had used anOther email previously

Try signing in again with you our Apple ID and Apple password I found that this works

every update by Apple renders the same problem

Turned my phone off and then on again and it worked fine after that.

I also found that using phone internet connection solves the problem, after trying all the iPad account setup advice in this thread. Weird, so I’m off to reboot my router now and see if that solves the issue.

Thank you very much! This resolved a problem I was having for months! I had turned SSL on without updating my ISPs port number for SSL!

I started having this issue after the latest upgrade. The only way I could resolve it was by deleting my POP accounts and re-entering them as IMAP accounts. You may have to change the name/description of the account, otherwise it might be detected as a duplicate account and it won't be saved.

I am using an iPhone XI pro max , IOS 13.3.1 and found a bug in the outgoing mail server . It says that the username and password are optional and they are not . Thought i can help.

put in the username and password under the outgoing server settings even though it says it's optional

This happened to me too. The only fix I found was switching to Outlook!!

This worked for me:

Settings > Passwords and Accounts > Click on your email > Click on your email again at the top > Outgoing Mail Server > Click Primary Server which is at the top.

Now make sure the info on this screen is filled out. Username/password/use SSL/Authentication should be password/check that the Port # is correct. (You may need to check with your ISP for the number.)

I fixed the problem following advice on this thread. On the email setup screen on the iPad you have to fill in 'optional details' on the smtp page.

Turn off the WIFI on your iPhone in settings

it works fine until the idiots at Apple fix it I think I will go back to Samsung

I am assuming you have called the Apple helpline for their assistance - sounds like you have a really strange issue - good luck!

I was getting the sender email invalid as well after updating to the 11. I deleted my mail account and re-added it. On the outgoing server, where it says user name and password optional, it isn't. Once I added it my mail would go through. My husband had the same problem, but he had the user name and password filled in. I told him to re-enter his password. The phone reverified, now he can send email.

Hope this works for others!!!