Cannot send emails using Thunderbird.

[#1]

Moved wifes emails to Thunderbird and can receive emails but can't send them.

Incoming and outgoing server settings are OK.

Email is to a domain that is hosted by plusnet and I have no issues with my emails thru the same domain on a different laptop using Thunderbird.

Router and ISP is not plusnet so I am using SMTP authentication - tried SSL/TLS & STARTTLS, normal password.

Not sure why, but Thunderbird asks for password when trying to send the email.

error message - The mail server responded <xxx@xxx.co.uk> sender rejected - invalid domain (no MX or A record)

Ran Telnet and got 235 authentication suceeded.

Can also send via webmail

Any ideas where I'm going wrong?

[#2]

Thunderbird has some oddities with configuring the SMTP server.  It is not a product I use, but I have fiddled with it.

Excellent testing using TELNET which proves that the userID and password were fine.

Email is to a domain that is hosted by plusnet

Where is the SENDING domain hosted?

Both you and the wife are sending as the same domain as in ...

• you@mydomain.co.uk
• wife@mydomain.co.uk

For the SMTP server login, what are you using for the wife's configuration

• wife@mydomain.co.uk
• wife@youraccount.plus.com
• youraccount+wife << preferred

The SMTP server is relay.plus.net port 587 encryption STARTTLS

Check the status of mydomain.co.uk here - MX Lookup Tool - Check your DNS MX Records online - MxToolbox

[#3]

Thunderbird has some oddities with configuring the SMTP server.  It is not a product I use, but I have fiddled with it.

Excellent testing using TELNET which proves that the userID and password were fine.

Email is to a domain that is hosted by plusnet

Where is the SENDING domain hosted? Same as the to domain - plusnet

Both you and the wife are sending as the same domain as in ...

• you@mydomain.co.uk
• wife@mydomain.co.uk Yes
  

For the SMTP server login, what are you using for the wife's configuration

• wife@mydomain.co.uk
• wife@youraccount.plus.com
• youraccount+wife << preferred This one
  

The SMTP server is relay.plus.net port 587 encryption STARTTLS Yes and also tried 465 SSL/TLS which works as my settings

Check the status of mydomain.co.uk here - MX Lookup Tool - Check your DNS MX Records online - MxToolbox

Results -  mx.avasin.plus.net, SMTP OK, Blacklist OK, No DMARC record found, DMARC Quarantine/Reject policy not enabled, DNS record found.

[#4]

See if anything here helps - How to Fix Thunderbird SMTP Error?

[#5]

@paul1098 if theres no luck from @Townman s link , then try setting Thunderbird to log smtp traffic https://kb.mozillazine.org/Session_logging_for_mail/news

[#6]

Thanks Townman,
I'll start working thru' the fixes and see if it gets resolved.

[#7]

@Townman 
Worked thru' those suggestions but nothing worked.

@MisterW 

Logged the smtp traffic but not sure what its telling me.