The campaign went out, but some recipients received an empty e-mail or a message in a language they do not read. The cause is always the same: the campaign content was not filled in for every event language, so recipients whose preferred language was the second one received the empty version.
Open the campaign, switch the content language with the flag in the top right corner, and look at the second language version. If it is empty, you have confirmed the cause.
A campaign is sent to each recipient in their preferred language. When a contact has no language set, the primary language of the event is used. Content, however, is filled in separately for each language — if you wrote the text in one version only, the other stays empty and goes out exactly like that.
It most often hits events where a language was added mid-preparation: the first campaigns were written when there was only one language, and nobody went back to fill them in after the second was added.
You cannot recall sent e-mails or rewrite their text. There are two realistic options:
Fill in the content and send again — copy the campaign with Copy, fill in the missing language in the copy, and send it targeted at the affected group only. You can target by preferred language or by the group those people belong to.
Write a short apology — on a small event with few recipients, one short message is usually cleaner than repeating the whole campaign.
A mailing that is still running can be deleted with the trash icon in the mailings table. A completed mailing cannot be deleted.
After writing a campaign, always switch the language and check the second version — it is the only check that catches this. Before the real send, use Test campaign to send both language variants to your own address.
When a contact has no language set, the e-mail goes out in the event's primary language — even if that person does not read it. Before sending, check the contact table for how many people have no language and fill it in.
An e-mail with no text and a blank or generic subject often does not even get opened, so you may not learn about the problem straight away. That is exactly why sending a test of both versions is worth it, not just the one you are currently writing.