Save mail message activity illegal characters in header field


I am using save mail message activity to save mail. But for few emails it is throwing error as illegal characters in header field. How to solve this?

Hi @Sailaja_Pasupuleti

Do you have multiple email id’s for some of the emails and single email id’s for some? And how do you join it?

When you have single email id you must not have “;” in it so might need to check on that.
Also could provide more information on you mail header?


I am reading emails using Get mail messages activity and saving email in .eml format using save mail message activity.

Also, email subject is having Chinese characters for failed mails.

Are you using Unicode type to save the mail?


I am using below activity

Can you try to save with .msg instead of .eml?

Still facing the same issue.


Did you identify which header item is caused?
If not, can you try to remove property of mailMessage one by one, then identify which is cause.


mailMessaegVar.Subject = ""

Then, save


Then save


The following is an image for the above.



Thanks for the steps. After updating UiPath.Mail.activities to latest version 1.18.2 the error gone. But now facing different issue. It’s working fine in dev machine but not in production machine. I have checked the packages in the prod machine, it is having 1.18.2. Still not sure why it is failing in prod machine.


What error do you have in prod machine? Is it same as this title’s error?


Yes same title error.


Is there any difference regarding .net framework such as Language pack etc. b/w dev and prod?


May I know how to verify .net framework components. I have verified machine language it is same.

I have verified following one

In dev - updated march 2023
In prod - last year 2022

Will it cause any issues

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