Addition to the above question: After turning Avast off, I now get this error:

Login to server smtp.gmail.com failed.

It then gives me the option to 'Enter New Password'. I had already verified that the stored password was correct, but I reentered it. It still failed. I have already checked all other parameters (outgoing server settings, etc.), comparing them also with the ones my husband has set. I have the same settings. His system works, mine does not.

I located something on the internet: https://forum.avast.com/index.php?topic=132204.0 Apparently, Avast is still using port to 25 to send emails that it's scanned (?) ... even when we specifically say to use a different port. As a Comcast user and an Avast user the only way I can get my outgoing emails to send is by turning off Avast's outgoing scan function. Access Avast's Mail Shield SETTINGS and deleting everything on the "SSL scanning" page.

So turning the scanning off was a good idea.

gmail SMTP server settings: Outgoing Server (SMTP: )smtp.gmail.com If using port: 587 Connection Security: STARTTLS

If using port: 465 Connection Security: SSL/TLS Authentication method: Normal Password Username = full email address for gmail Password: same password used to access gmail webmail

TRy removing the stored password. Tools > Options > Security > Passwords tab click on 'Saved passwords' click on 'Show passwords' select the smtp password for the account. click on 'REmove' click on close click on OK Restart Thunderbird. Try to send email to your husband. If it prompts for password, enter correct password used to access gmail webmail.

Are your ports blocked for outbound mail? 587/465 or is port 25 blocked by your ISP?