diff --git a/src/dialogs/certifywidget.cpp b/src/dialogs/certifywidget.cpp
index c6fe68501..ded38879e 100644
--- a/src/dialogs/certifywidget.cpp
+++ b/src/dialogs/certifywidget.cpp
@@ -1,566 +1,580 @@
 /*  dialogs/certifywidget.cpp
 
     This file is part of Kleopatra, the KDE keymanager
     SPDX-FileCopyrightText: 2019 g 10code GmbH
 
     SPDX-License-Identifier: GPL-2.0-or-later
 */
 
 #include <config-kleopatra.h>
 
 #include "certifywidget.h"
 
 #include "kleopatra_debug.h"
 
 #include <KLocalizedString>
 #include <KConfigGroup>
 #include <KSeparator>
 #include <KSharedConfig>
 
 #include <Libkleo/DefaultKeyFilter>
 #include <Libkleo/KeySelectionCombo>
 #include <Libkleo/Formatting>
 #include <Libkleo/KeyCache>
 #include <Libkleo/Predicates>
 
 #include <QCheckBox>
 #include <QHBoxLayout>
 #include <QLabel>
 #include <QLineEdit>
 #include <QListView>
 #include <QParallelAnimationGroup>
 #include <QPropertyAnimation>
 #include <QPushButton>
 #include <QScrollArea>
 #include <QStandardItemModel>
 #include <QToolButton>
 #include <QToolTip>
 #include <QVBoxLayout>
 
 #include <gpgme++/key.h>
 
 #include <gpgme++/gpgmepp_version.h>
 #if GPGMEPP_VERSION >= 0x10E00 // 1.14.0
 # define GPGME_HAS_REMARKS
 #endif
 
 using namespace Kleo;
 
 namespace {
 
 // Maybe move this in its own file
 // based on code from StackOverflow
 class AnimatedExpander: public QWidget
 {
     Q_OBJECT
 public:
     explicit AnimatedExpander(const QString &title = QString(),
                               QWidget *parent = nullptr);
     void setContentLayout(QLayout *contentLayout);
 
 private:
     QGridLayout mainLayout;
     QToolButton toggleButton;
     QFrame headerLine;
     QParallelAnimationGroup toggleAnimation;
     QScrollArea contentArea;
     int animationDuration{300};
 };
 
 AnimatedExpander::AnimatedExpander(const QString &title, QWidget *parent):
     QWidget(parent)
 {
     toggleButton.setStyleSheet(QStringLiteral("QToolButton { border: none; }"));
     toggleButton.setToolButtonStyle(Qt::ToolButtonTextBesideIcon);
     toggleButton.setArrowType(Qt::ArrowType::RightArrow);
     toggleButton.setText(title);
     toggleButton.setCheckable(true);
     toggleButton.setChecked(false);
 
     headerLine.setFrameShape(QFrame::HLine);
     headerLine.setFrameShadow(QFrame::Sunken);
     headerLine.setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Maximum);
 
     contentArea.setStyleSheet(QStringLiteral("QScrollArea { border: none; }"));
     contentArea.setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Fixed);
 
     // start out collapsed
     contentArea.setMaximumHeight(0);
     contentArea.setMinimumHeight(0);
 
     // let the entire widget grow and shrink with its content
     toggleAnimation.addAnimation(new QPropertyAnimation(this, "minimumHeight"));
     toggleAnimation.addAnimation(new QPropertyAnimation(this, "maximumHeight"));
     toggleAnimation.addAnimation(new QPropertyAnimation(&contentArea, "maximumHeight"));
 
     mainLayout.setVerticalSpacing(0);
     mainLayout.setContentsMargins(0, 0, 0, 0);
     int row = 0;
     mainLayout.addWidget(&toggleButton, row, 0, 1, 1, Qt::AlignLeft);
     mainLayout.addWidget(&headerLine, row++, 2, 1, 1);
     mainLayout.addWidget(&contentArea, row, 0, 1, 3);
     setLayout(&mainLayout);
     QObject::connect(&toggleButton, &QToolButton::clicked, [this](const bool checked) {
         toggleButton.setArrowType(checked ? Qt::ArrowType::DownArrow : Qt::ArrowType::RightArrow);
         toggleAnimation.setDirection(checked ? QAbstractAnimation::Forward : QAbstractAnimation::Backward);
         toggleAnimation.start();
     });
 }
 
 void AnimatedExpander::setContentLayout(QLayout *contentLayout)
 {
     delete contentArea.layout();
     contentArea.setLayout(contentLayout);
     const auto collapsedHeight = sizeHint().height() - contentArea.maximumHeight();
     auto contentHeight = contentLayout->sizeHint().height();
     for (int i = 0; i < toggleAnimation.animationCount() - 1; ++i) {
         auto expanderAnimation = static_cast<QPropertyAnimation *>(toggleAnimation.animationAt(i));
         expanderAnimation->setDuration(animationDuration);
         expanderAnimation->setStartValue(collapsedHeight);
         expanderAnimation->setEndValue(collapsedHeight + contentHeight);
     }
     auto contentAnimation = static_cast<QPropertyAnimation *>(toggleAnimation.animationAt(toggleAnimation.animationCount() - 1));
     contentAnimation->setDuration(animationDuration);
     contentAnimation->setStartValue(0);
     contentAnimation->setEndValue(contentHeight);
 }
 
 class SecKeyFilter: public DefaultKeyFilter
 {
 public:
     SecKeyFilter() : DefaultKeyFilter()
     {
         setRevoked(DefaultKeyFilter::NotSet);
         setExpired(DefaultKeyFilter::NotSet);
         setHasSecret(DefaultKeyFilter::Set);
         setCanCertify(DefaultKeyFilter::Set);
         setIsOpenPGP(DefaultKeyFilter::Set);
     }
 };
 
 class UserIDModel : public QStandardItemModel
 {
     Q_OBJECT
 public:
     enum Role {
         UserIDIndex = Qt::UserRole
     };
     explicit UserIDModel(QObject *parent = nullptr) : QStandardItemModel(parent) {}
 
     GpgME::Key certificateToCertify() const
     {
         return m_key;
     }
 
     void setKey(const GpgME::Key &key)
     {
         m_key = key;
         clear();
         const std::vector<GpgME::UserID> ids = key.userIDs();
         int i = 0;
         for (const auto &uid: key.userIDs()) {
             if (uid.isRevoked() || uid.isInvalid()) {
                 // Skip user ID's that cannot really be certified.
                 i++;
                 continue;
             }
             auto const item = new QStandardItem;
             item->setText(Formatting::prettyUserID(uid));
             item->setData(i, UserIDIndex);
             item->setCheckable(true);
             item->setEditable(false);
             item->setCheckState(Qt::Checked);
             appendRow(item);
             i++;
         }
     }
 
     void setCheckedUserIDs(const std::vector<unsigned int> &uids)
     {
         std::vector<unsigned int> sorted = uids;
         std::sort(sorted.begin(), sorted.end());
         for (int i = 0, end = rowCount(); i != end; ++i) {
             item(i)->setCheckState(std::binary_search(sorted.begin(), sorted.end(), i) ? Qt::Checked : Qt::Unchecked);
         }
     }
 
     std::vector<unsigned int> checkedUserIDs() const
     {
         std::vector<unsigned int> ids;
         for (int i = 0; i < rowCount(); ++i) {
             if (item(i)->checkState() == Qt::Checked) {
                 ids.push_back(item(i)->data(UserIDIndex).toUInt());
             }
         }
         qCDebug(KLEOPATRA_LOG) << "Checked uids are: " << ids;
         return ids;
     }
 
 private:
     GpgME::Key m_key;
 };
 
 static bool uidEqual(const GpgME::UserID &lhs, const GpgME::UserID &rhs)
 {
     return qstrcmp(lhs.parent().primaryFingerprint(),
                     rhs.parent().primaryFingerprint()) == 0
             && qstrcmp(lhs.id(), rhs.id()) == 0;
 }
 
 auto checkBoxSize(const QCheckBox *checkBox)
 {
     QStyleOptionButton opt;
     return checkBox->style()->sizeFromContents(QStyle::CT_CheckBox, &opt, QSize(), checkBox);
 }
 
 auto createInfoButton(const QString &text, QWidget *parent)
 {
     auto infoBtn = new QPushButton{parent};
     infoBtn->setIcon(QIcon::fromTheme(QStringLiteral("help-contextual")));
     infoBtn->setFlat(true);
 
     QObject::connect(infoBtn, &QPushButton::clicked, infoBtn, [infoBtn, text] () {
         QToolTip::showText(infoBtn->mapToGlobal(QPoint()) + QPoint(infoBtn->width(), 0),
                            text, infoBtn, QRect(), 30000);
     });
 
     return infoBtn;
 }
 
 }
 
 class CertifyWidget::Private
 {
 public:
     Private(CertifyWidget *qq)
         : q{qq}
         , mFprLabel{new QLabel{q}}
         , mSecKeySelect{new KeySelectionCombo{/* secretOnly= */true, q}}
         , mExportCB{new QCheckBox{q}}
         , mPublishCB{new QCheckBox{q}}
         , mTagsLE{new QLineEdit{q}}
         , mTrustSignatureCB{new QCheckBox{q}}
         , mTrustSignatureDomainLE{new QLineEdit{q}}
     {
         auto mainLay = new QVBoxLayout{q};
         mainLay->addWidget(mFprLabel);
 
         auto secKeyLay = new QHBoxLayout{q};
         secKeyLay->addWidget(new QLabel(i18n("Certify with:")));
 
         mSecKeySelect->setKeyFilter(std::shared_ptr<KeyFilter>(new SecKeyFilter()));
 
         secKeyLay->addWidget(mSecKeySelect, 1);
         mainLay->addLayout(secKeyLay);
 
         mainLay->addWidget(new KSeparator{Qt::Horizontal, q});
 
         auto listView = new QListView{q};
         listView->setModel(&mUserIDModel);
         mainLay->addWidget(listView, 1);
 
         // Setup the advanced area
         auto expander = new AnimatedExpander{i18n("Advanced"), q};
         mainLay->addWidget(expander);
 
         auto advLay = new QVBoxLayout{q};
 
         mExportCB->setText(i18n("Certify for everyone to see (exportable)"));
         advLay->addWidget(mExportCB);
 
         {
             auto layout = new QHBoxLayout{q};
 
             mPublishCB->setText(i18n("Publish on keyserver afterwards"));
             mPublishCB->setEnabled(mExportCB->isChecked());
 
             layout->addSpacing(checkBoxSize(mExportCB).width());
             layout->addWidget(mPublishCB);
 
             advLay->addLayout(layout);
         }
 
 #ifndef GPGME_HAS_REMARKS
         mTagsLE->setVisible(false);
 #else
         {
             auto tagsLay = new QHBoxLayout{q};
 
             mTagsLE->setPlaceholderText(i18n("Tags"));
             auto infoBtn = createInfoButton(i18n("You can use this to add additional info to a certification.") +
                                             QStringLiteral("<br/><br/>") +
                                             i18n("Tags created by anyone with full certification trust "
                                                 "are shown in the keylist and can be searched."),
                                             q);
 
             tagsLay->addWidget(new QLabel{i18n("Tags:"), q});
             tagsLay->addWidget(mTagsLE, 1);
             tagsLay->addWidget(infoBtn);
 
             advLay->addLayout(tagsLay);
         }
 #endif
 
 #ifndef QGPGME_SUPPORTS_TRUST_SIGNATURES
         mTrustSignatureCB->setVisible(false);
         mTrustSignatureDomainLE->setVisible(false);
 #else
         {
             auto layout = new QHBoxLayout{q};
 
             mTrustSignatureCB->setText(i18n("Certify as trusted introducer"));
             auto infoBtn = createInfoButton(i18n("You can use this to certify a trusted introducer for a domain.") +
                                             QStringLiteral("<br/><br/>") +
                                             i18n("All certificates with email addresses belonging to the domain "
                                                  "that have been certified by the trusted introducer are treated "
                                                  "as certified, i.e. a trusted introducer acts as a kind of "
                                                  "intermediate CA for a domain."),
                                             q);
 
             layout->addWidget(mTrustSignatureCB, 1);
             layout->addWidget(infoBtn);
 
             advLay->addLayout(layout);
         }
         {
             auto layout = new QHBoxLayout{q};
 
             mTrustSignatureDomainLE->setPlaceholderText(i18n("Domain"));
             mTrustSignatureDomainLE->setEnabled(mTrustSignatureCB->isChecked());
 
             layout->addSpacing(checkBoxSize(mTrustSignatureCB).width());
             layout->addWidget(mTrustSignatureDomainLE);
 
             advLay->addLayout(layout);
         }
 #endif
 
         expander->setContentLayout(advLay);
 
         connect(&mUserIDModel, &QStandardItemModel::itemChanged, q, &CertifyWidget::changed);
 
         connect(mExportCB, &QCheckBox::toggled, [this] (bool on) {
             mPublishCB->setEnabled(on);
         });
 
         connect(mSecKeySelect, &KeySelectionCombo::currentKeyChanged, [this] (const GpgME::Key &) {
 #ifdef GPGME_HAS_REMARKS
             updateTags();
 #endif
             Q_EMIT q->changed();
         });
 
         connect(mTrustSignatureCB, &QCheckBox::toggled, q, [this] (bool on) {
             mTrustSignatureDomainLE->setEnabled(on);
             Q_EMIT q->changed();
         });
         connect(mTrustSignatureDomainLE, &QLineEdit::textChanged, q, &CertifyWidget::changed);
 
         loadConfig();
     }
 
     ~Private() = default;
 
     void loadConfig()
     {
         const KConfigGroup conf(KSharedConfig::openConfig(), "CertifySettings");
         mSecKeySelect->setDefaultKey(conf.readEntry("LastKey", QString()));
         mExportCB->setChecked(conf.readEntry("ExportCheckState", false));
         mPublishCB->setChecked(conf.readEntry("PublishCheckState", false));
     }
 
     void updateTags()
     {
         if (mTagsLE->isModified()) {
             return;
         }
 #ifdef GPGME_HAS_REMARKS
         GpgME::Key remarkKey = mSecKeySelect->currentKey();
 
         if (!remarkKey.isNull()) {
             std::vector<GpgME::UserID> uidsWithRemark;
             QString remark;
             for (const auto &uid: mTarget.userIDs()) {
                 GpgME::Error err;
                 const char *c_remark = uid.remark(remarkKey, err);
                 if (c_remark) {
                     const QString candidate = QString::fromUtf8(c_remark);
                     if (candidate != remark) {
                         qCDebug(KLEOPATRA_LOG) << "Different remarks on user ids. Taking last.";
                         remark = candidate;
                         uidsWithRemark.clear();
                     }
                     uidsWithRemark.push_back(uid);
                 }
             }
             // Only select the user ids with the correct remark
             if (!remark.isEmpty()) {
                 selectUserIDs(uidsWithRemark);
             }
             mTagsLE->setText(remark);
         }
 #endif
     }
 
+    void updateTrustSignatureDomain()
+    {
+        if (mTrustSignatureDomainLE->text().isEmpty() && mTarget.numUserIDs() == 1) {
+            // try to guess the domain to use for the trust signature
+            const auto address = mTarget.userID(0).addrSpec();
+            const auto atPos = address.find('@');
+            if (atPos != std::string::npos) {
+                const auto domain = address.substr(atPos + 1);
+                mTrustSignatureDomainLE->setText(QString::fromUtf8(domain.c_str(), domain.size()));
+            }
+        }
+    }
+
     void setTarget(const GpgME::Key &key)
     {
         mFprLabel->setText(i18n("Fingerprint: <b>%1</b>",
                             Formatting::prettyID(key.primaryFingerprint())) + QStringLiteral("<br/>") +
                             i18n("<i>Only the fingerprint clearly identifies the key and its owner.</i>"));
         mUserIDModel.setKey(key);
         mTarget = key;
 
         updateTags();
+        updateTrustSignatureDomain();
     }
 
     GpgME::Key secKey() const
     {
         return mSecKeySelect->currentKey();
     }
 
     void selectUserIDs(const std::vector<GpgME::UserID> &uids)
     {
         const auto all = mTarget.userIDs();
 
         std::vector<unsigned int> indexes;
         indexes.reserve(uids.size());
 
         for (const auto &uid: uids) {
             const unsigned int idx =
                 std::distance(all.cbegin(), std::find_if(all.cbegin(), all.cend(),
                             [uid](const GpgME::UserID &other) { return uidEqual(uid, other); }));
             if (idx < all.size()) {
                 indexes.push_back(idx);
             }
         }
 
         mUserIDModel.setCheckedUserIDs(indexes);
     }
 
     std::vector<unsigned int> selectedUserIDs() const
     {
         return mUserIDModel.checkedUserIDs();
     }
 
     bool exportableSelected() const
     {
         return mExportCB->isChecked();
     }
 
     bool publishSelected() const
     {
         return mPublishCB->isChecked();
     }
 
     QString tags() const
     {
         return mTagsLE->text().trimmed();
     }
 
     GpgME::Key target() const
     {
         return mTarget;
     }
 
     bool isValid() const
     {
         static const QRegularExpression domainNameRegExp{QStringLiteral(R"(^\s*((xn--)?[a-z0-9]+(-[a-z0-9]+)*\.)+[a-z]{2,}\s*$)"),
                                                          QRegularExpression::CaseInsensitiveOption};
 
         // do not accept null keys
         if (mTarget.isNull() || mSecKeySelect->currentKey().isNull()) {
             return false;
         }
         // do not accept empty list of user ids
         if (selectedUserIDs().empty()) {
             return false;
         }
         // do not accept if the keys are the same
         if (_detail::ByFingerprint<std::equal_to>()(mTarget, mSecKeySelect->currentKey())) {
             return false;
         }
         if (mTrustSignatureCB->isChecked() && !domainNameRegExp.match(mTrustSignatureDomainLE->text()).hasMatch()) {
             return false;
         }
         return true;
     }
 
 public:
     CertifyWidget *const q;
     QLabel *mFprLabel = nullptr;
     KeySelectionCombo *mSecKeySelect = nullptr;
     QCheckBox *mExportCB = nullptr;
     QCheckBox *mPublishCB = nullptr;
     QLineEdit *mTagsLE = nullptr;
     QCheckBox *mTrustSignatureCB = nullptr;
     QLineEdit *mTrustSignatureDomainLE = nullptr;
 
     UserIDModel mUserIDModel;
     GpgME::Key mTarget;
 };
 
 CertifyWidget::CertifyWidget(QWidget *parent)
     : QWidget{parent}
     , d{std::make_unique<Private>(this)}
 {
 }
 
 Kleo::CertifyWidget::~CertifyWidget() = default;
 
 void CertifyWidget::setTarget(const GpgME::Key &key)
 {
     d->setTarget(key);
 }
 
 GpgME::Key CertifyWidget::target() const
 {
     return d->target();
 }
 
 void CertifyWidget::selectUserIDs(const std::vector<GpgME::UserID> &uids)
 {
     d->selectUserIDs(uids);
 }
 
 std::vector<unsigned int> CertifyWidget::selectedUserIDs() const
 {
     return d->selectedUserIDs();
 }
 
 GpgME::Key CertifyWidget::secKey() const
 {
     return d->secKey();
 }
 
 bool CertifyWidget::exportableSelected() const
 {
     return d->exportableSelected();
 }
 
 QString CertifyWidget::tags() const
 {
     return d->tags();
 }
 
 bool CertifyWidget::publishSelected() const
 {
     return d->publishSelected();
 }
 
 bool CertifyWidget::trustSignatureSelected() const
 {
     return d->mTrustSignatureCB->isChecked();
 }
 
 QString CertifyWidget::trustSignatureDomain() const
 {
     return d->mTrustSignatureDomainLE->text().trimmed();
 }
 
 bool CertifyWidget::isValid() const
 {
     return d->isValid();
 }
 
 // For UserID model
 #include "certifywidget.moc"