Lets see... you email two people both as To: in an email... one get it the other does not. Clearly the problem is with the recipient end of the equation or neither would get it.

The most probable cause is the recipient has a poor spam setup and may perhaps be only getting mail from folks in their address book. I would check their spam settings and folder for the missing mail. (that is where about 90% of missing mail is usually found)

When you check your sent folder on gmail, the mail will be there saying it was sent. That leaves Thunderbird out of the sending equation as Google say they sent it. There is no evidence to indicate it was not sent. Only that the recipient can't find it. At this point we do not know if the email was delivered by their mail provider or they treated it as spam.

BTW if your ISP is suggesting incompatibility you might want to look for a better provider. All internet connections are covered by standards. Google is not all that compliant, but what they are telling you is about the same as if you ring them at say googles web site does not render in chrome and they suggest an incompatibility

BTW if your ISP is suggesting incompatibility you might want to look for a better provider. All internet connections are covered by standards. Google is not all that compliant, but what they are telling you is about the same as if you ring them at say googles web site does not render in chrome and they suggest an incompatibility </blockquote>

Hi Matt!

Thank you very much for your reply! Very interesting and easy to understand!

Re: the above quote -- please forgive me, I was unclear in my initial choice of words. It was a technician at my local PC repair shop that suggested incompatibility, not my Internet service provider (ISP). By ISP, do you mean broadband provider or email provider?

At this point I am inclined to agree with you, it could very well be a spam problem at the recipient end. Maybe my recipient, a busy person, did not check the spam folder thoroughly. I´ll try sending another test email and see what happens.

I also spoke to the recipient´s workplace IT service desk. They had no indications about email problems.

Further re: item 4/ in my initial post. The recipient receives emails sent directly from my Gmail outbox, and I received the answer in my Gmail inbox, but not emails via TB-through-Gmail. Is it common for spam filters to treat emails sent through TB as spam, regardless of which internet provider it is?

You did not comment on 5/ above, so as a TB layperson I´ll refrain from touching the Gmail SMTP settings (if indeed they are available to Gmail users).

Again, many thanks for your help!

When you send the email, do you send the email in both plain text and html ? Suggest this is worth checking.

• Menu app icon > Options
• select 'Composition'
• Scroll to 'HTML Style' section
• click on 'Send Options'

When sending messages in html format.....

• from drop down select 'Send the mesage in both plain text and html'
• click on OK.

Then try sending the email.

Hi Toad-Hall!

Thank you very much for your reply!

To reply to your question -- I usually send emails only in plain text. But I really appreciate that you direct me to the option of sending emails in both plain text and html format. Seems very useful indeed!

An update to my original question -- on Jan. 22, I sent another test email, in plain text, to recipient. Email was sent without any error message. Today, I received a reply from the recipient, with no indication of problems at recipient´s end. I replied in turn and did not get any error message.

Another question -- are spam filters especially sensitive to emails sent via TB through Gmail or any other email provider?

Thank you very much in advance for any additional info!