E-mail Attachment Generation Error

When trying to attach pdf to email, the attachment was not successfully generated, and email cannot be sent.
The shortcode I use for attachment is [e2pdf-attachment id="3"], as form action email in formidable.
If I use [e2pdf-download id="3"], works fine; also attachment worked when it was in Pro2PDF.

Thanks,
Mo

Hi.

Are you getting any error messages? Do you get email without any attachments? Or email just not received at all?

We remain at your service.

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We would really appreciate your feedback at WordPress.org!

Email just not send at all, No error message.
If I go to one of the entries in formidable, click "Resend", a normal email would be shown as "sent to [email protected]", but with attachment, it only shows as "sent to".
I had E2Pdf debug enabled, no error message found there, no error message found in WordPress debug log, either.
I use WP Mail Log to log outgoing emails, the attached file is a screenshot from its log.

We could not replicate an issue. I see that WP Mail Log marked messages as with Error. Is there any useful information when you click on "View" ?

Unfortunately we will need access to website to investigate fully issue. If it's possible you can complete this form so we can check.

Another solution - you can check out error.log of website, maybe there will be some information which will help us to replicate issue.

We remain at your service.

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We would really appreciate your feedback at WordPress.org!

We've just sent you reply to your email. It seems the problem in settings of your SMTP server about attachment size.

We remain at your service.

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We would really appreciate your feedback at WordPress.org!