mpack & sendmail problems

I wrote a script ages ago that sends me an email automatically when some function is satisfied. It has worked well but failed recently, with a message appended suggesting that I visit my mail provider’s website that explains the problem.
Although my application uses mpack, I show below an example using sendmail to demonstrate the problem. I’ve changed my email address and mail provider for security, but keeping the same formats.

Terminal command

keith@T500:~$ echo “Subject: sendmail test” | sendmail -v [email protected]
[<-] 220 mailfront20.emailco ESMTP Exim 4.90_1 Ubuntu Wed, 01 Jan 2020 17:06:01 +0100
[->] EHLO T500
[<-] 250 HELP
[<-] 334 VXNlcm5hbWU6
[->] a2VpdGhfc3RhbW1lcnNAcnVuYm94LmNvbQ==
[<-] 334 UGFzc3dvcmQ6
[<-] 235 Authentication succeeded
[->] MAIL FROM:[email protected]
[<-] 250 OK
[->] RCPT TO:[email protected]
[<-] 250 Accepted
[->] DATA
[<-] 354 Enter message, ending with “.” on a line by itself
[->] Received: by T500 (sSMTP sendmail emulation); Wed, 01 Jan 2020 16:06:01 +0000
[->] From: “keith” [email protected]
[->] Date: Wed, 01 Jan 2020 16:06:01 +0000
[->] Subject: sendmail test
[->] .
[<-] 550 Invalid From address. Please see
sendmail: 550 Invalid From address. Please see

You will see at the end the complaint that the From address is wrong and is rejected by my mail company following their updated security measures. The correct address is shown on the “RCPT TO:” line but in the active line where the correct address needs to be the address has been shortened: “MAIL FROM: [email protected]”. And perhaps the other “From” line needs to be correct as well.

My email provider now requires that the from address is not an alias and the sSMTP.conf file (shown below) shows my base address correctly (as it always was). I have even tried changing the Thunderbird default address back to the base address. So I can’t understand why it has been changed in two places in sendmail.

Contents of etc/ssmtp/ssmtp.conf

Config file for sSMTP sendmail

The person who gets all mail for userids < 1000

Make this empty to disable rewriting.

[email protected]

The place where the mail goes. The actual machine name is required no

MX records are consulted. Commonly mailhosts are named


[email protected]
AuthPass={my password}

Where will the mail seem to come from?


The full hostname


Are users allowed to set their own From: address?

YES - Allow the user to specify their own From: address

NO - Use the system generated From: address


I would be very grateful for any advice.