Where in your account are you receiving this error message? I have taken a look at your account and can see your most recent campaign was successfully sent. We have however seen cases of users getting this error when scheduling their email campaign when the subject line contains an ampersand, letter, and semicolon (e.g., "A&B;"). Is that the case for your experience as well? If so, we suggest removing any instances of these & characters, letters, or semicolons from the subject line and rewording it to not have those characters in that order.
Frankie.P Community & Social Media Support
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