# Error when sending E-Mail to certain providers because of SMTP protocol violation **URL:** \ **Category:** Other native modules\ **Tags:** Issue\ **Created:** [March 3, 2025, 8:05pm UTC](https://www.dolibarr.org/forum/t/error-when-sending-e-mail-to-certain-providers-because-of-smtp-protocol-violation/30053 "2025-03-03T20:05:00Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![sn0b4ll](https://www.dolibarr.org/forum/letter_avatar_proxy/v4/letter/s/6de8d8/32.png) [@sn0b4ll](https://www.dolibarr.org/forum/u/sn0b4ll)\ **Post date:** [March 3, 2025, 8:05pm UTC](https://www.dolibarr.org/forum/t/error-when-sending-e-mail-to-certain-providers-because-of-smtp-protocol-violation/30053/1 "2025-03-03T20:05:00Z")
Hey there, since my update to 20.3 mails send by dolibarr bounce when sending invoices via E-Mail to certain customers. The error I get on the failed delivery report mail is: `SMTP error from remote server for TEXT command, host: smtpin.rzone.de (81.169.145.97) reason: 554 5.6.0 SMTP protocol violation: A header line must be terminated by CRLF` It seems like certain Mail-Service-Providers (here Strato) are blocking the E-Mails, while others (Telekom, Proton, [Web.de](http://Web.de)) are accepting the messages. I suspect that Dolibarr is encoding the Mail-Header in an non RFC-Compliant way, since Stratro recently started enforcing RFCs more strictly. Did anyone of you also have a similar problem and / or has a solution? Many thanks! Greetings, sn0b4ll Edit: Typos ---
**Author:** ![jonbendtsen](https://www.dolibarr.org/forum/letter_avatar_proxy/v4/letter/j/977dab/32.png) [@jonbendtsen](https://www.dolibarr.org/forum/u/jonbendtsen)\ **Post date:** [March 3, 2025, 10:29pm UTC](https://www.dolibarr.org/forum/t/error-when-sending-e-mail-to-certain-providers-because-of-smtp-protocol-violation/30053/2 "2025-03-03T22:29:57Z")
oh, where do you see the error report? does it bounce back to you, or is it in the mailserver log? ---
**Author:** ![sn0b4ll](https://www.dolibarr.org/forum/letter_avatar_proxy/v4/letter/s/6de8d8/32.png) [@sn0b4ll](https://www.dolibarr.org/forum/u/sn0b4ll)\ **Post date:** [March 3, 2025, 10:41pm UTC](https://www.dolibarr.org/forum/t/error-when-sending-e-mail-to-certain-providers-because-of-smtp-protocol-violation/30053/3 "2025-03-03T22:41:46Z")
Hey đź‘‹ it bounces back to my mail account. The sending itself looks fine, seeing no errors in the logs of dolibarr. ---
**Author:** ![jonbendtsen](https://www.dolibarr.org/forum/letter_avatar_proxy/v4/letter/j/977dab/32.png) [@jonbendtsen](https://www.dolibarr.org/forum/u/jonbendtsen)\ **Post date:** [March 4, 2025, 7:28am UTC](https://www.dolibarr.org/forum/t/error-when-sending-e-mail-to-certain-providers-because-of-smtp-protocol-violation/30053/4 "2025-03-04T07:28:40Z")
does it state which header is the issue? My expectation is that it is a PHP library that actually sends the email, which PHP version are you running? Could it be something that your SMTP server adds before sending it on? ---
**Author:** ![sn0b4ll](https://www.dolibarr.org/forum/letter_avatar_proxy/v4/letter/s/6de8d8/32.png) [@sn0b4ll](https://www.dolibarr.org/forum/u/sn0b4ll)\ **Post date:** [March 4, 2025, 5:22pm UTC](https://www.dolibarr.org/forum/t/error-when-sending-e-mail-to-certain-providers-because-of-smtp-protocol-violation/30053/5 "2025-03-04T17:22:42Z")
Hey 👋 sadly no, just that overall error and afterwards the mail itself. I noticed that the subject and nail addresses are encoded in utf-8, while they should be ASCII according to the RFC? But that’s a wild guess from my side. I can give you feedback on the version in the upcoming days, but I am using the docker version. I will check when I am at the location again. The SMTP server is not the problem, I am able to send mails via Thunderbird and the same credentials to addresses that bounce when addressed via dolibarr :confused: ---
**Author:** ![jonbendtsen](https://www.dolibarr.org/forum/letter_avatar_proxy/v4/letter/j/977dab/32.png) [@jonbendtsen](https://www.dolibarr.org/forum/u/jonbendtsen)\ **Post date:** [March 4, 2025, 6:10pm UTC](https://www.dolibarr.org/forum/t/error-when-sending-e-mail-to-certain-providers-because-of-smtp-protocol-violation/30053/6 "2025-03-04T18:10:59Z")
If you use the docker image, there is no reason to supply the PHP version, that can be inferred from the docker image. Okay, that does not seem to be a SMTP server issue - through probably IP address and/or username is different for your Thunderbird and your Dolibarr. I think you should report the issue on github as a bug, and include as much information as possible. > **[Dolibarr/dolibarr](https://github.com/Dolibarr/dolibarr/issues)** > > Dolibarr ERP CRM is a modern software package to manage your company or foundation's activity (contacts, suppliers, invoices, orders, stocks, agenda, accounting, ...). it's an open source W... ---
**Author:** ![Joey](https://www.dolibarr.org/forum/letter_avatar_proxy/v4/letter/j/f14d63/32.png) [@Joey](https://www.dolibarr.org/forum/u/Joey)\ **Post date:** [March 10, 2025, 8:16pm UTC](https://www.dolibarr.org/forum/t/error-when-sending-e-mail-to-certain-providers-because-of-smtp-protocol-violation/30053/7 "2025-03-10T20:16:49Z")
I had a similar issue after dolibarr update from 19.0.2 to 20.0.3 with following Error using Strato Server "error during sending E-Mail (Sender=my company[my@domain.com](mailto:my@domain.com), [Receiver=me@domain.com](mailto:Receiver=me@domain.com)) Error [120]: Ran into problems sending Mail. Response: 554 5.6.0 SMTP protocol violation: A header line must be terminated by CRLF " i changed from SMTP/SMTPS socket library (works on 19.0.2) to Swift Mailer socket library (works on 20.0.3) all other settings remain the same. brgds Joey ---
**Author:** ![Dolisupport.nl](https://www.dolibarr.org/forum/user_avatar/www.dolibarr.org/dolisupport.nl/32/3564_2.png) [@Dolisupport.nl](https://www.dolibarr.org/forum/u/Dolisupport.nl)\ **Post date:** [March 26, 2026, 2:49pm UTC](https://www.dolibarr.org/forum/t/error-when-sending-e-mail-to-certain-providers-because-of-smtp-protocol-violation/30053/8 "2026-03-26T14:49:59Z")
I had the same issue and debugged. I found in my installation that I had MAIN\_FIX\_FOR\_BUGGED\_MTA set to 1. This setting removes crlf lines for bugged providers, but I had a correct provider that checks on correct crlf lines. So in Setup→Other settings I added MAIN\_FIX\_FOR\_BUGGED\_MTA to 0 with description “Set to zero for correct crlf line”. And it works again with regular smtp.