So verify that your firewall or antivirus are not blocking it, setting up a proper exception rule. I've read others are having the same issue with Thunderbird and Office365, so I'm in the process of canceling Office365 and moving to more compatible email system. Sometimes an outgoing mail server can conflict with the computer’s protection systems. STARTTLS and 587 are the configuration values for sending via. Control your antivirus or firewall settings.You can use then port 587 or 465 for more information read our article about SMTP ports. The outgoing mail server uses normally port 25, but some ISPs may block it due to the increasing spam traffic that’s been passing through it. Here’s a list of all the SMTP error codes to get your bearings and remember again that using a professional outgoing server this won’t happen again. Now this is trickier: even if your SMTP details are correct, the server itself can be down or not functioning for some reason. Another small mistake that happens usually, so doublecheck your login details. To find out yours, please refer to our list of the most common ones or ask directly your provider. This is an extremely common mistake: you have set up your mail client with the wrong SMTP parameters. So first of all, be sure that you’re connected to the internet! That is why it’s always better to rely on a professional server, even if you don’t have big mailing needs: for instance turboSMTP offers a handy free plan of 6.000 emails/month, lifetime.Īnd here’s a checklist to understand why you’re unable to send emails and troubleshoot any major problem: If you can’t send your emails, the problem is very likely (but not exclusively) related to your SMTP server – the server taking care of the whole email delivery process.

You open your favorite mail client or software (Mozilla Thunderbird, Outlook Express, SendBlaster…), write a few lines, insert the recipients’ addresses, click “Send” and… An error is returned. Sometimes it happens: you simply cannot send emails.

Thunderbird email not sending