Thunderbird changes outgoing email address

Question

Composing a new email:
In the "To" field I start to type an address. Thunderbird provides a drop-down of matches from my address book. I select one of the addresses. Thunderbird puts it into the "To" field. At this point, my cursor is still in the "To" field. Then I hit Enter to move to the next field, & Thunderbird changes the email address to a different address (a different address from my address book).
If I add a space after the email address before pressing Enter, Thunderbird leaves the email address as is.
Behavior is kind of random - address is not replaced all the time. Also, for a while Thunderbird will make one change - like always changing address X to address Y, then it will switch to another change - always replacing address Z with address W.
The replacement address is always one that is in the address book.
Also, Thunderbird randomly colors some outgoing email addresses as red, even though they are in my address book.

Answer 1

hi jbh01
The easiest method is to use the contacts sidebar as described in option 2.
But contacts do need to be in an Address Book.
However, if your issue is to reveal more TO fields, then you can drag the divider downwards. See image below.
If you write using Plain Text , there will be no Formatting Bar. If you use HTML formatting, then there will be a Formatting Bar.
In the image below there is a Formatting Bar between 'Subject' and the composing area. In the image below, I've indicated this with a red line.
Use mouse and hover over this line, the mouse should chnage to a double headed arrow. Left click and hold down to grab the line. Then move mouse downwards to move the line. It will reveal more TO fields.