''JudeRon [[#question-1091081|said]]'' <blockquote>…the Incoming server settings are identical on the 2 accounts EXCEPT user name & email address…</blockquote> Just to make sure I understand you; you have two email accounts/addresses with the same provider? You say your problems are with your phone. How do you expect a forum for Thunderbird to be able to help you? You mentioned a "Thunderbird (sub)account". * There's no such thing as a "Thunderbird account"; your email account is provided and operated by an email provider, which might be your ISP, your cellphone operator or one of the well-known services such as gmail, gmx, outlook.com etc. * Thunderbird doesn't recognize any distinction between accounts and sub-accounts. Every email address is considered to be unique, even if it's an alias. A server, however might deliver messages addressed to multiple addresses (possibly your sub-accounts) to a single Inbox. * Either an SMTP server requires a login or it doesn't. Whether you're using a "main account" or alternatively a "sub account" doesn't affect the ''sending'' of messages. Some providers offer different settings for mobile use vs computer use. There's generally no reason why mobile/phone settings shouldn't also work on a computer, but computer settings, intended for use at home connected to your ISP may not work on a mobile device that needs to connect via other networks. Having the same settings on the phone as you have on the computer may actually be part of your problem. Typically, the settings for mobile use would demand a login for sending, whereas the connection for use at home may not, since it could have identified and validated you via your internet connection. Generally, I would try to use the mobile settings in preference to the others, and particularly so on portable devices such as tablets, phones, laptops or netbooks.